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Safety Tool

Supplement-Drug Interaction Checker

Drug interactions for 20 common supplements. Search by supplement or by drug name.

20Supplements
15Timing rules

Stop 2 weeks before surgery

Discontinue these supplements at least 2 weeks before any elective surgical procedure to reduce bleeding risk: Fish Oil / Omega-3, St. John's Wort, Vitamin E, Turmeric / Curcumin, Ginkgo Biloba, Garlic Supplements.

Fish Oil / Omega-3stop before surgery

Medication review

This source review is incomplete. It does not establish which combinations are safe or appropriate for you.

Warfarin (Coumadin)

Source review required

The reviewed sources do not establish one bleeding or INR effect for every fish-oil product. A warfarin case report and a small controlled study had different findings.

Have the prescribing team review the exact omega-3 product and decide on bleeding or INR monitoring. Warfarin dose changes require the prescriber's instructions. The linked LOVAZA label covers monitoring with prescription EPA/DHA ethyl esters. Other mechanism and risk statements in this entry still need source review.

Evidence for prescription EPA/DHA ethyl esters does not establish the same effect for every fish-oil supplement.

FDA label, DailyMed set ID 21cfa4ce-0b05-47ed-b268-339eb1b83b75 (LOVAZA, section 7.1; monitoring/action only; legacy mechanism and risk pending source review)

Clopidogrel (Plavix)

Source review required

The cited observational study included aspirin as well as clopidogrel and did not find a statistically significant bleeding difference. It does not establish the risk of every fish-oil and clopidogrel combination.

Review the exact omega-3 product with the prescribing team. The LOVAZA label calls for periodic monitoring when prescription EPA/DHA ethyl esters are used with antiplatelet medicines; it does not establish a monitoring plan for every fish-oil supplement.

The cited prescription products have different formulations. Their precautions do not establish a monitoring plan for every fish-oil supplement.

High-dose Aspirin

Source review required

The reviewed trials do not establish a high-dose aspirin interaction estimate or a fish-oil dose cutoff for this entry. ASCEND studied 100 mg aspirin and 1-g omega-3 capsules; those exposures do not validate this high-dose aspirin claim.

The prescribing team needs the aspirin dose and exact omega-3 formulation before giving monitoring or procedure instructions. This entry supplies no universal 3-g cutoff or stop-before-surgery instruction.

The available studies do not define a high-dose aspirin threshold for this interaction. Findings for low-dose aspirin or one prescription omega-3 product cannot establish the effect of other doses or formulations.

Blood pressure medications

Source review required

Blood-pressure effects vary by omega-3 preparation. The reviewed evidence does not establish a predictable benefit or hypotension risk for every blood-pressure medicine.

Have the prescribing team review the exact omega-3 product and blood-pressure medicine, including whether monitoring is needed.

General blood-pressure findings do not establish the effect of combining a particular omega-3 product with a named medicine.

Orlistat (Alli)

Source review required

Orlistat reduces fat absorption. The reviewed omega-3 study measured formulation-specific absorption, not clinical effectiveness or a validated two-hour schedule.

Review the exact omega-3 formulation and timing with the pharmacist or prescribing team. The two-hour XENICAL label instruction concerns fat-soluble vitamin supplements, not a validated fish-oil schedule.

The vitamin-spacing instruction in the XENICAL label is not a fish-oil timing rule. The exact product and formulation matter.

Other combinations awaiting review (9)

  • Fish Oil with Anticoagulants

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Omega-3 fish oil high-dose with Warfarin

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Omega-3 fish oil high-dose with Clopidogrel

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Fish Oil with Aspirin

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Omega-3 fish oil high-dose with Aspirin

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Omega-3 (EPA/DHA) with Lisinopril

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Omega-3 (EPA/DHA) with Losartan

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Omega-3 (EPA/DHA) with Ramipril

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

  • Omega-3 (EPA/DHA) with Valsartan

    Source review required

    The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

View full Fish Oil / Omega-3 research page
St. John's Wortstop before surgery

The most interaction-prone supplement in common use. St. John's Wort induces multiple drug-metabolism enzymes and can cause treatment failure across many drug classes.

SSRIs (Prozac, Zoloft, Lexapro)

  • St. John's Wort with SSRIscritical

    Do not combine

    Do not stop your medicine. Ask your prescriber before taking this supplement.

    Serotonin syndrome, seizures, rhabdomyolysis.

    Additive serotonergic activity. St. John's Wort inhibits serotonin reuptake similarly to SSRIs; combined use produces excessive serotonergic stimulation.

SNRIs (Effexor, Cymbalta)

  • St. John's Wort with Venlafaxinecritical

    Ask your prescriber first

    PMID 15260917

Oral contraceptives

ActionNever combine. Use backup contraception.

SourcePMID 19719333

Cyclosporine

  • St. John's Wort with Cyclosporinecritical

    Do not combine

    Do not stop your medicine. Ask your prescriber before taking this supplement.

    Acute organ rejection requiring return to dialysis; a 29-year-old kidney/pancreas transplant recipient developed chronic rejection after cyclosporine levels became subtherapeutic.

    St. John's Wort induces CYP3A4 isoenzyme activity and P-glycoprotein (P-gp) expression in the liver and small intestines, accelerating cyclosporine metabolism and reducing its absorption, leading to subtherapeutic concentrations.

    PMID 10981246

  • St. John's Wort with Tacrolimuscritical

    Do not combine

    Do not stop your medicine. Ask your prescriber before taking this supplement.

    PMID 15260917

Warfarin

  • St. John's Wort with Warfarinhigh

    St. John's Wort significantly reduces the pharmacological effect of warfarin, leading to a decreased international normalized ratio (INR) and potentially increasing the risk of thrombosis.

    St. John's Wort induces the apparent clearance of both S-warfarin and R-warfarin by inducing cytochrome P450 (CYP) enzymes, particularly CYP3A4 and CYP2C9, which are responsible for warfarin metabolism.

    PMID 15089812

ActionNever combine.

SourcePMID 19719333

Chemotherapy agents

  • St. John's Wort with Imatinibcritical

    Do not combine

    Do not stop your medicine. Ask your prescriber before taking this supplement.

    Concomitant St. John's Wort reduced imatinib AUC by 30%. Avoid the combination.

    PMID 15470331

  • HIV protease inhibitors (ritonavir, indinavir)

    Induces CYP3A4, reducing drug levels. Treatment failure and viral rebound.

    ActionNever combine.

  • Digoxin

    Induces P-glycoprotein, reducing digoxin levels. Heart failure from subtherapeutic levels.

    ActionNever combine.

  • Theophylline

    Induces CYP1A2, reducing levels. Loss of asthma or COPD control.

    ActionAvoid.

  • Triptans (sumatriptan)

    Additive serotonergic effect. Serotonin syndrome risk.

    ActionAvoid.

Stop 2 weeks before surgery

Anesthesia interactions from CYP enzyme induction.

View full St. John's Wort research page
Magnesium6 timing

Fluoroquinolone antibiotics (Cipro, Levaquin)

  • Magnesium with Fluoroquinolones/Tetracyclinesmoderate

    Take at different times

    Take ciprofloxacin at least 2 hours before or 6 hours after magnesium. Take levofloxacin at least 2 hours before or after magnesium. Take moxifloxacin at least 4 hours before or 8 hours after magnesium. For any other fluoroquinolone or a tetracycline, ask your pharmacist how far apart to take them, because magnesium reduces how much of the antibiotic is absorbed.

    Reduced absorption and bioavailability of the antibiotic, potentially leading to decreased systemic exposure and treatment failure against bacterial infections.

    Magnesium ions form insoluble chelates with fluoroquinolones and tetracyclines in the gastrointestinal tract. This complexation prevents the antibiotic from being absorbed across the intestinal mucosa.

    PMID 33919271

Tetracycline antibiotics

  • Magnesium with Fluoroquinolones/Tetracyclinesmoderate

    Take at different times

    Take ciprofloxacin at least 2 hours before or 6 hours after magnesium. Take levofloxacin at least 2 hours before or after magnesium. Take moxifloxacin at least 4 hours before or 8 hours after magnesium. For any other fluoroquinolone or a tetracycline, ask your pharmacist how far apart to take them, because magnesium reduces how much of the antibiotic is absorbed.

    Reduced absorption and bioavailability of the antibiotic, potentially leading to decreased systemic exposure and treatment failure against bacterial infections.

    Magnesium ions form insoluble chelates with fluoroquinolones and tetracyclines in the gastrointestinal tract. This complexation prevents the antibiotic from being absorbed across the intestinal mucosa.

    PMID 33919271

Bisphosphonates (Fosamax, Boniva)

  • Magnesium with Bisphosphonatesmoderate

    Take at different times

    Take alendronate at least 30 minutes before magnesium. Take ibandronate at least 60 minutes before magnesium. For risedronate or any other bisphosphonate, ask your pharmacist how far apart to take them, because magnesium reduces how much of the bisphosphonate is absorbed.

    Decreased absorption and bioavailability of bisphosphonates, potentially reducing their efficacy in treating osteoporosis.

    Magnesium and other divalent cations physically bind to bisphosphonates in the gastrointestinal tract through chelation. This forms an insoluble complex that prevents the bisphosphonate from being absorbed into the bloodstream.

    PMID 26934925

  • Levothyroxine (Synthroid)

    Magnesium binds levothyroxine in the gut, reducing absorption. Subtherapeutic thyroid hormone levels.

    ActionSeparate by 4 or more hours.

  • Muscle relaxants and sedatives

    Additive CNS depression. Excessive drowsiness.

    ActionUse caution, especially with magnesium taken at night.

  • Potassium-sparing diuretics

    Both raise serum magnesium and potassium. Hypermagnesemia.

    ActionMonitor electrolytes.

Timing Separation Rules

  • Levothyroxine4 hours
  • Oral ciprofloxacin tablets + magnesium-containing antacidsTake ciprofloxacin at least 2 hours before or 6 hours after the antacid.
    Timing instruction sourcesCiprofloxacin tablets, section 2.4
  • Oral levofloxacin tablets + magnesium-containing antacidsTake levofloxacin at least 2 hours before or 2 hours after the antacid.
    Timing instruction sourcesLevofloxacin tablets, section 2.4
  • Oral moxifloxacin tablets + magnesium-containing products listed in its labelTake moxifloxacin at least 4 hours before or 8 hours after the magnesium-containing product.
    Timing instruction sourcesMoxifloxacin tablets, section 2.2
  • Other antibiotic, formulation or magnesium productAsk your pharmacist for the interval for your exact products.
  • Bisphosphonates2+ hours after bisphosphonate
View full Magnesium research page
Calcium3 timing

Levothyroxine (Synthroid)

  • Calcium with Levothyroxinehigh

    Take at different times

    Separate from thyroid hormone dose by at least 4 hours. Take Levothyroxine on an empty stomach 30 to 60 minutes before food, coffee, or supplements.

    Concurrent administration of calcium carbonate and levothyroxine can lead to reduced levothyroxine absorption and increased serum thyrotropin levels, potentially causing hypothyroidism.

    Take Levothyroxine at least 4 hours apart from calcium-containing supplements. Calcium can reduce Levothyroxine absorption by 20 to 40 percent and cause under-replacement.

    Levothyroxine adsorbs to calcium carbonate in an acidic environment, such as the stomach, which reduces its bioavailability and absorption.

    PMID 10838651

  • Calcium with Levothyroxinemoderate

    Calcium carbonate taken with levothyroxine significantly lowered free and total T4 and raised TSH. One in five patients moved above the normal TSH range. Separate doses by four hours.

    PMID 10838651

Fluoroquinolones (Cipro)

  • Calcium with Ciprofloxacincritical

    Take at different times

    Take ciprofloxacin at least 2 hours before or 6 hours after calcium.

    PMID 12092748

  • Calcium with Fluoroquinolonesmoderate

    The formation of stable fluoroquinolone-calcium chelates decreases the absorption rate and systemic exposure of the antibiotic, leading to significant reductions in pharmacokinetic parameters such as C_max and AUC, which can impair therapeutic efficacy.

    Fluoroquinolones interact with multivalent metal cations like calcium in the gastrointestinal tract to form stable, insoluble chelates. This chelation reduces the oral bioavailability of the antibiotic by preventing its absorption across the intestinal mucosa.

    PMID 33919271

  • Tetracycline and doxycycline

    Calcium chelates the antibiotic. Antibiotic treatment failure.

    ActionSeparate by 2 to 3 hours.

  • Iron supplements

    Calcium blocks iron absorption. Iron deficiency.

    ActionTake at different meals.

  • Bisphosphonates (Fosamax)

    Calcium blocks bisphosphonate absorption. Reduced bone drug efficacy.

    ActionTake bisphosphonate on an empty stomach; calcium later.

  • Thiazide diuretics (HCTZ)

    Both increase serum calcium. Hypercalcemia.

    ActionMonitor calcium levels.

Timing Separation Rules

  • Levothyroxine4 hours
  • Tetracycline / fluoroquinolone antibiotics2 to 3 hours
  • Bisphosphonates2+ hours after bisphosphonate
View full Calcium research page
Vitamin K

Vitamin K is the direct pharmacological antagonist of warfarin. Supplementing without cardiology supervision can cause dangerous clots.

Warfarin (Coumadin)

  • Vitamin K2 (MK-7) with Warfarinhigh

    MK-7 supplementation may reduce warfarin effectiveness more than equivalent K1 dose due to longer tissue retention. INR monitoring required when starting or stopping MK-7.

    MK-7 is more potent INR-lowering than K1 at similar doses. Avoid initiating without prescriber awareness.

    Vitamin K2 menaquinone-7 has long half-life and accumulates more than K1. Even modest MK-7 doses (45 to 180 mcg per day) can antagonize warfarin and lower INR.

    PMID 34406879

  • Vitamin K1 (phylloquinone) with Warfarinhigh

    High-dose vitamin K1 supplementation (over 100 mcg per day) can reverse warfarin anticoagulation, reducing INR and increasing thrombosis risk. Inconsistent vitamin K intake causes INR fluctuations. Standard advice: maintain consistent daily vitamin K intake; avoid high-dose vitamin K supplements unless prescribed for warfarin reversal.

    Vitamin K1 directly antagonizes warfarin. Avoid high-dose vitamin K supplements (over 100 mcg) without prescriber guidance. Maintain consistent vitamin K dietary intake to stabilize INR.

    Vitamin K1 (phylloquinone) is the direct substrate antagonized by warfarin. Warfarin inhibits VKORC1 to prevent vitamin K recycling. Exogenous vitamin K1 directly reverses warfarin anticoagulation.

    PMID 16499407

  • Vitamin K with Warfarinhigh

    Decreased sensitivity to warfarin, leading to lower INR and a requirement for higher maintenance doses of warfarin to achieve adequate anticoagulation.

    Vitamin K directly antagonizes the pharmacodynamic effect of warfarin, which acts as a vitamin K antagonist by inhibiting the vitamin K epoxide reductase complex, thereby overcoming the drug's inhibition of vitamin K-dependent clotting factor synthesis.

ActionKeep vitamin K intake consistent (do not suddenly increase or decrease). Do not supplement vitamin K without cardiologist approval.
    View full Vitamin K research page
    Vitamin Estop before surgery

    Warfarin and other anticoagulants

    • Vitamin E high-dose with Warfarinhigh

      The adult upper limit is 1,000 mg a day, but bleeding risk has been reported below it. Trials found more hemorrhagic stroke at 50 mg a day, and at 400 IU every other day in people who were mostly also taking aspirin. This matters most if you take a blood thinner.

      High-dose vitamin E (over 400 IU per day) increases bleeding risk in warfarin users. Limit vitamin E to nutritional doses (under 100 IU) while on warfarin and monitor for bleeding signs.

      Vitamin E doses over 400 IU per day increase bleeding risk with warfarin. Limit to nutritional doses (under 100 IU).

      Alpha-tocopherol at over 400 IU per day inhibits platelet aggregation. Large RCT data show increased bleeding risk in anticoagulated patients.

      PMID 40065887

    • Vitamin E with Anticoagulantsmoderate

      High-dose vitamin E intake can cause serious bleeding events when taken with anticoagulants.

      High-dose vitamin E intake inhibits vitamin K-derived coagulation factor synthesis.

      PMID 36949518

    ActionMonitor INR.

    Aspirin and NSAIDs

    The adult upper limit is 1,000 mg a day, but bleeding risk has been reported below it. Trials found more hemorrhagic stroke at 50 mg a day, and at 400 IU every other day in people who were mostly also taking aspirin. This matters most if you take a blood thinner.

    • Vitamin E high-dose with Aspirinmoderate

      Observational data suggest additive bleeding risk with aspirin. Monitor for unusual bleeding.

      Vitamin E high-dose has antiplatelet activity that is observationally additive to aspirin.

      PMID 40065887

    ActionUse caution at high doses.

    Chemotherapy (alkylating agents)

    • Vitamin E with Cyclophosphamidecritical

      Do not combine

      Do not stop your medicine. Ask your prescriber before taking this supplement.

      PMID 31855498

    • Statins combined with niacin

      High-dose vitamin E may blunt the HDL-raising effect of the statin-niacin combo. Reduced cardiovascular benefit.

      ActionClinical significance unclear.

    Stop 2 weeks before surgery

    High-dose bleeding risk.

    View full Vitamin E research page
    Iron3 timing

    Levothyroxine

    • Iron with Levothyroxinehigh

      Take at different times

      Separate from thyroid hormone dose by at least 4 hours. Take Levothyroxine on an empty stomach 30 to 60 minutes before food, coffee, or supplements.

      Simultaneous ingestion of ferrous sulfate and thyroxine causes a variable reduction in thyroxine efficacy that is clinically significant in some patients, leading to hypothyroidism.

      Take Levothyroxine at least 4 hours apart from iron supplements. Iron can reduce Levothyroxine absorption by 30 to 50 percent.

      Iron binds to levothyroxine in the gastrointestinal tract, forming an insoluble complex that reduces the absorption and bioavailability of the thyroid hormone.

      PMID 1443969

    Tetracycline and doxycycline

    • Iron with Fluoroquinolones/Tetracyclinesmoderate

      Take at different times

      Take ciprofloxacin at least 2 hours before or 6 hours after iron. Take levofloxacin at least 2 hours before or after iron. Take moxifloxacin at least 4 hours before or 8 hours after iron. For any other fluoroquinolone or a tetracycline, ask your pharmacist how far apart to take them, because iron reduces how much of the antibiotic is absorbed.

      Concomitant use of iron supplements and fluoroquinolones or tetracyclines significantly impairs the oral absorption and bioavailability of the antibiotics, potentially leading to treatment failure.

      Iron forms insoluble chelates with fluoroquinolones and tetracyclines in the gastrointestinal tract. This chelation prevents the absorption of both the antibiotic and the iron into the bloodstream.

      PMID 8474934

    Fluoroquinolones

    • Iron with Fluoroquinolones/Tetracyclinesmoderate

      Take at different times

      Take ciprofloxacin at least 2 hours before or 6 hours after iron. Take levofloxacin at least 2 hours before or after iron. Take moxifloxacin at least 4 hours before or 8 hours after iron. For any other fluoroquinolone or a tetracycline, ask your pharmacist how far apart to take them, because iron reduces how much of the antibiotic is absorbed.

      Concomitant use of iron supplements and fluoroquinolones or tetracyclines significantly impairs the oral absorption and bioavailability of the antibiotics, potentially leading to treatment failure.

      Iron forms insoluble chelates with fluoroquinolones and tetracyclines in the gastrointestinal tract. This chelation prevents the absorption of both the antibiotic and the iron into the bloodstream.

      PMID 8474934

    • Antacids, PPIs, H2 blockers

      Reduced stomach acid impairs iron absorption. Iron deficiency persists.

      ActionTake iron on an empty stomach or with vitamin C. Separate from antacids by 2 or more hours.

    • Levodopa (Parkinson's)

      Iron reduces levodopa absorption. Worsened Parkinson's symptoms.

      ActionSeparate by 2 or more hours.

    • Methyldopa

      Iron reduces absorption. Subtherapeutic blood pressure control.

      ActionSeparate by 2 or more hours.

    Timing Separation Rules

    • Levothyroxine4 hours
    • Tetracycline / fluoroquinolone antibiotics2 to 3 hours
    • Antacids and PPIs2 hours
    View full Iron research page
    Zinc1 timing

    Fluoroquinolone antibiotics

    • Zinc with Ciprofloxacincritical

      Take at different times

      Take ciprofloxacin at least 2 hours before or 6 hours after zinc.

      PMID 2610494

    Penicillamine (Wilson's disease)

    • Zinc with Penicillaminemoderate

      Take at different times

      Take penicillamine at least 1 hour apart from zinc, on an empty stomach.

      Concurrent administration of zinc and penicillamine may result in decreased gastrointestinal absorption and diminished therapeutic effects of penicillamine.

      Zinc, a polyvalent cation, can chelate with penicillamine in the gastrointestinal tract, forming a nonabsorbable complex that reduces the absorption of both agents.

      PMID 151717

    • Tetracycline antibiotics

      Zinc chelates the antibiotic. Reduced antibiotic efficacy.

      ActionSeparate by 2 to 3 hours.

    • Copper (chronic high-dose zinc)

      Zinc over 40mg/day induces metallothionein, which sequesters copper. Copper deficiency leading to anemia and neutropenia.

    Timing Separation Rules

    • Tetracycline / fluoroquinolone antibiotics2 to 3 hours
    View full Zinc research page
    Turmeric / Curcuminstop before surgery

    Warfarin and other anticoagulants

    • Turmeric/Curcumin with Blood Thinnerslow

      Curcumin has antiplatelet activity in laboratory studies. No study examines it with any anticoagulant or antiplatelet drug; an additive effect is theoretical.

      Curcumin and its derivatives prolong activated partial thromboplastin time (aPTT) and prothrombin time (PT) by inhibiting the generation of thrombin and activated factor X (FXa). This antiplatelet and anticoagulant activity potentiates the effects of blood-thinning medications.

      PMID 22531131

    • Turmeric and curcumin high-dose with Warfarinlow

      This row describes concentrated turmeric or curcumin supplements rather than a specific dose, not turmeric used in cooking.

      Theoretical mild additive antiplatelet effect. Limited published case reports.

      Curcumin has weak antiplatelet effects and may inhibit CYP2C9 in vitro. Clinical impact at standard supplement doses uncertain.

    Aspirin and NSAIDs

    • Turmeric/Curcumin with Blood Thinnerslow

      Curcumin has antiplatelet activity in laboratory studies. No study examines it with any anticoagulant or antiplatelet drug; an additive effect is theoretical.

      Curcumin and its derivatives prolong activated partial thromboplastin time (aPTT) and prothrombin time (PT) by inhibiting the generation of thrombin and activated factor X (FXa). This antiplatelet and anticoagulant activity potentiates the effects of blood-thinning medications.

      PMID 22531131

    • Turmeric and curcumin high-dose with Aspirinlow

      This row describes concentrated turmeric or curcumin supplements rather than a specific dose, not turmeric used in cooking.

      Theoretical additive antiplatelet effect with aspirin. Monitor for bruising or unusual bleeding.

      Turmeric and curcumin high-dose has antiplatelet activity that is additive to aspirin's COX-1 inhibition.

      PMID 36288911

    Diabetes medications (metformin, sulfonylureas)

    • Curcumin with Metformincompatible

      No interaction concern with metformin. No benefit is claimed.

      Curcumin has weak CYP and P-gp modulation effects in vitro. Metformin is not significantly metabolized by CYP enzymes; clinical interaction unlikely.

    CYP3A4 substrates

    This row describes concentrated turmeric or curcumin supplements rather than a specific dose, not turmeric used in cooking.

    • Turmeric and curcumin high-dose with Losartanlow

      Generally minor. Monitor BP with high-dose supplementation.

      High-dose curcumin has anti-inflammatory and mild antihypertensive activity. Weak CYP modulation in vitro.

      PMID 37567790

    • Turmeric and curcumin high-dose with Bisoprolollow

      Theoretical mild interaction. Clinically minor.

      High-dose curcumin has weak CYP modulation in vitro. Bisoprolol interaction theoretical.

      PMID 40322036

    • Tacrolimus or cyclosporine

      CYP3A4 inhibition may raise levels. Toxicity risk.

      ActionAvoid or monitor drug levels.

      Basis: Theoretical

    Stop 2 weeks before surgery

    High-dose antiplatelet effect.

    View full Turmeric / Curcumin research page
    Ashwagandha

    Levothyroxine and thyroid medications

    • Ashwagandha with Levothyroxinemoderate

      The interaction can lead to iatrogenic thyrotoxicosis, presenting with symptoms such as supraventricular tachycardia, due to excessive thyroid hormone levels.

      Ashwagandha root extract is postulated to stimulate thyroidal activity by increasing the synthesis and/or release of thyroxine (T4) at the glandular level. Additionally, some Ashwagandha supplements may contain clinically relevant amounts of T3 and T4, further elevating thyroid hormone concentrations.

      PMID 35475098

    ActionMonitor thyroid function. Dose adjustment may be needed.

    SourcePMID 28829155

    Immunosuppressants (cyclosporine, tacrolimus, prednisone)

    • Ashwagandha with Immunosuppressantshigh

      Ashwagandha may counteract the intended effects of immunosuppressant medications, leading to reduced suppression of the immune system and potential organ rejection or disease flare-ups.

      Ashwagandha has immunostimulatory properties that activate both the innate and adaptive arms of the immune system, enhancing overall immune function. This immune stimulation can counteract the effects of immunosuppressive drugs like cyclophosphamide or dexamethasone.

      PMID 10616957

    ActionAvoid in transplant patients and autoimmune patients.

    Diabetes medications

    • Ashwagandha with Metforminlow

      Monitor thyroid function if both initiated together; clinically significant interaction with metformin not expected.

      Ashwagandha may modulate thyroid axis (typically T4 increase) and HPA axis. No direct metformin interaction.

      PMID 38003702

    • Sedatives and benzodiazepines (Xanax, Valium)

      Additive CNS depression. Excessive sedation.

      ActionUse caution. Reduce ashwagandha dose if you feel drowsy.

    • Blood pressure medications

      Ashwagandha may lower BP. Hypotension.

      ActionMonitor BP.
    View full Ashwagandha research page
    Berberine

    Metformin

    • Berberine with Metforminhigh

      Co-administration of berberine and metformin can lead to an additive hypoglycemic effect, increasing the risk of hypoglycemia.

      Berberine inhibits the transport activity of organic cation transporters (OCT1 and OCT2), which govern the disposition of metformin, thereby increasing the plasma concentration and systemic exposure of metformin.

      PMID 35209140

    • Berberine with Metforminmoderate

      PMID 18442638

    ActionMonitor glucose closely. Metformin dose may need to be reduced.

    SourcePMID 37439907

    CYP2D6 substrates (codeine, tramadol, many antidepressants)

    • Berberine with Metoprolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Metoprolol pharmacokinetic interaction theoretical.

      PMID 21678521

    • Berberine with Carvedilollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Carvedilol pharmacokinetic interaction theoretical.

      PMID 21678521

    • Berberine with Propranolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Propranolol pharmacokinetic interaction theoretical.

      PMID 21678521

    • Berberine with Nebivolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Nebivolol pharmacokinetic interaction theoretical.

      PMID 21678521

    CYP3A4 substrates (statins, calcium channel blockers)

    • Berberine with Losartanmoderate

      Additive BP lowering and minor pharmacokinetic shift. Monitor blood pressure when starting or stopping berberine in losartan users.

      Berberine has demonstrated mild blood pressure lowering effects and modulates CYP2C9 and CYP3A4 in vitro. Combined effect with losartan can be additive (BP) and pharmacokinetic (metabolite ratio shift).

      PMID 7902181

    • Berberine with Bisoprolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Bisoprolol pharmacokinetic interaction theoretical.

      PMID 21678521

    ActionUse caution with narrow-therapeutic-index drugs.

    SourcePMID 37439907

    Blood pressure medications

    • Berberine with Lisinoprilmoderate

      Additive blood pressure lowering possible. May be beneficial in some patients but increases risk of hypotension, especially at initiation or dose changes of either agent.

      Berberine has demonstrated mild blood pressure lowering effects in clinical trials, likely through endothelial nitric oxide modulation and additive RAAS effects. Co-administration with lisinopril may produce additive blood pressure reduction.

      PMID 14567065

    • Berberine with Losartanmoderate

      Additive BP lowering and minor pharmacokinetic shift. Monitor blood pressure when starting or stopping berberine in losartan users.

      Berberine has demonstrated mild blood pressure lowering effects and modulates CYP2C9 and CYP3A4 in vitro. Combined effect with losartan can be additive (BP) and pharmacokinetic (metabolite ratio shift).

      PMID 7902181

    • Berberine with Metoprolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Metoprolol pharmacokinetic interaction theoretical.

      PMID 21678521

    Show 4 more
    • Berberine with Carvedilollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Carvedilol pharmacokinetic interaction theoretical.

      PMID 21678521

    • Berberine with Propranolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Propranolol pharmacokinetic interaction theoretical.

      PMID 21678521

    • Berberine with Nebivolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Nebivolol pharmacokinetic interaction theoretical.

      PMID 21678521

    • Berberine with Bisoprolollow

      Theoretical mild interaction. Clinically minor at supplement doses.

      Berberine has weak CYP2D6 and CYP3A4 inhibitory effects in vitro. Bisoprolol pharmacokinetic interaction theoretical.

      PMID 21678521

    ActionMonitor BP.

    • Cyclosporine

      Berberine inhibits CYP3A4 and P-glycoprotein, dramatically increasing cyclosporine levels. Cyclosporine toxicity (nephrotoxic).

      ActionNever combine without transplant team supervision.

    • Sulfonylureas (glipizide, glyburide)

      Additive glucose lowering. Hypoglycemia.

      ActionMonitor blood sugar closely.

    • Anticoagulants

      Berberine may have antiplatelet effects. Bleeding risk.

      ActionMonitor if combining.
    View full Berberine research page
    CoQ10

    Medication review

    This source review is incomplete. It does not establish which combinations are safe or appropriate for you.

    Warfarin

    Source review required

    The evidence is limited and conflicting. It does not establish a severity grade, a uniform effect, a warfarin dose change or equivalence with ubiquinol.

    CoQ10 may affect warfarin response. A case report described reduced responsiveness, while a small four-week crossover trial found stable INR and no change in mean warfarin dose. These findings do not establish the same effect for every dose, preparation or patient.

    If you take warfarin, discuss starting or stopping CoQ10 with your prescriber, including whether INR monitoring should change.

    Prescriber discussion of starting or stopping CoQ10 and whether monitoring should change; no target INR, schedule or warfarin dose instruction.

    Blood pressure medications

    Source review required

    The reviewed sources do not establish interaction risks or benefits for the named blood-pressure medicines. They do not support medicine dose reduction, CoQ10 repletion instructions or a compatibility grade.

    This limited review does not establish interaction risks between CoQ10 and blood-pressure medicines.

    The reviewed source does not assess individual blood-pressure medicines or reduced-form CoQ10 (ubiquinol). It does not establish medicine dose reduction or a compatibility rating.

    Chemotherapy

    Source review required

    Individual cancer-treatment regimens and supplement formulations have not been assessed. The official source does not establish a universal effect or the proposed cancer-cell protection mechanism.

    NCCIH notes that CoQ10 may be incompatible with some cancer treatments. This review has not assessed individual treatment regimens.

    Discuss CoQ10 use with the oncology team before combining it with cancer treatment.

    Discussion with the oncology team; no instruction to change cancer treatment.

    • Coenzyme Q10

      Official source snapshot reviewed; this does not establish all claims in this entry.

    Insulin and diabetes medications

    Source review required

    The official caution concerns insulin. Other diabetes medicines remain unassessed. No insulin-sensitivity benefit or hypoglycemia frequency is established.

    NCCIH lists a possible interaction between CoQ10 and insulin. This review does not establish its likelihood, dose relationship or applicability to other diabetes medicines.

    Discuss combined use with the clinician who prescribes your insulin.

    The source names insulin. It does not establish an interaction risk or benefit for metformin or other diabetes medicines.

    • Coenzyme Q10

      Official source snapshot reviewed; this does not establish all claims in this entry.

    Other combinations awaiting review (26)

    • Coenzyme Q10 with Warfarin

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 supplementation with Warfarin

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Nebivolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Bisoprolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Labetalol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Carvedilol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Ramipril

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Losartan

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • CoQ10 with Enalapril

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • CoQ10 with Ramipril

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • CoQ10 with Losartan

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • CoQ10 with Valsartan

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • CoQ10 with Telmisartan

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Lisinopril

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Atenolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Carvedilol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Nebivolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Bisoprolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Labetalol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Metoprolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Propranolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Atenolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Metoprolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Propranolol

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Ubiquinol (reduced CoQ10) with Metformin

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    • Coenzyme Q10 with Metformin

      Source review required

      The risk, benefit, preparation and dose context for this recorded combination remain under review. This entry does not establish that the combination is safe.

    View full CoQ10 research page
    Ginkgo Bilobastop before surgery

    Warfarin and other anticoagulants

    • Ginkgo biloba with Warfarinlow

      Two controlled studies in healthy volunteers found ginkgo did not alter warfarin pharmacokinetics or INR. Bleeding case reports exist; stop before surgery and tell your clinician. For DOACs no study exists and the same low posture applies (mechanism_inference).

      Ginkgolides inhibit platelet activating factor (PAF). Case reports document spontaneous bleeding (intracranial, subdural, retinal) in patients on warfarin plus Ginkgo.

      PMID 22097347

    Aspirin and NSAIDs

    • Ginkgo Biloba with Antiplateletshigh

      Increased risk of bleeding and abnormal coagulation profiles.

      Ginkgo biloba extract inhibits platelet-activating factor (PAF), leading to synergistic antiplatelet effects when combined with antiplatelet drugs.

      PMID 18214851

    • Ginkgo biloba with Aspirinlow

      Case reports of bleeding events. Monitor for unusual bleeding when combining.

      Ginkgolides inhibit platelet activating factor (PAF). Additive antiplatelet effect with aspirin's COX-1 inhibition.

      PMID 41155474

    ActionAvoid combination.

    CYP2C9 substrates

    • Ginkgo biloba with Losartanlow

      Possible minor additive vascular effects. Monitor if combined with other antiplatelet or antihypertensive agents.

      Ginkgo biloba has mild vasodilatory and antiplatelet activity. Generally minor interaction with Losartan.

      PMID 38264278

    • Seizure medications (valproate, phenytoin)

      Ginkgo may lower seizure threshold. Breakthrough seizures.

      ActionAvoid in epilepsy patients.

      Basis: Case reports

    Stop 2 weeks before surgery

    Bleeding risk from PAF inhibition.

    View full Ginkgo Biloba research page
    Melatonin

    Diabetes medications

    • Melatonin with Diabetes Medicationsmoderate

      Melatonin supplementation may alter blood glucose levels and interfere with the effectiveness of diabetes medications, requiring potential dosage adjustments.

      Melatonin decreases insulin secretion by inhibiting cAMP and cGMP pathways while activating the phospholipaseC/IP3 pathway via MT1 and MT2 receptors. This interference with insulin secretion can affect glucose regulation and the efficacy of antidiabetic drugs.

      PMID 26331226

    ActionMonitor glucose.

    • Warfarin and other anticoagulants

      Melatonin may enhance anticoagulant effect. Increased bleeding risk.

      ActionMonitor INR.

      Basis: Case reports

    • Immunosuppressants

      Melatonin stimulates immune function. May counteract immunosuppression.

      ActionAvoid in transplant patients.

    • Sedatives and benzodiazepines

      Additive CNS depression. Excessive sedation.

      ActionUse lower doses of both.

    • Fluvoxamine (Luvox)

      Fluvoxamine inhibits CYP1A2, dramatically increasing melatonin levels. Excessive sedation and vivid dreams.

      ActionFluvoxamine strongly slows the breakdown of melatonin and raises its levels in the body. Ask your prescriber before taking them together.

      SourcePMID 11270913

    View full Melatonin research page
    N-Acetyl Cysteine (NAC)1 timing

    Medication review

    This source review is incomplete. It does not establish which combinations are safe or appropriate for you.

    Nitroglycerin

    Source review required

    The likelihood of harm with other doses, formulations and populations remains unassessed. The oral study does not establish a routine oral-supplement hypotension rate or a blanket instruction to avoid the combination.

    Severe headaches were reported more often with oral NAC plus nitroglycerin patches than with patches alone in one trial in adults with unstable angina. A separate hospital study reported symptomatic low blood pressure with intravenous NAC plus intravenous nitroglycerin. These findings do not establish the risk from routine oral supplements.

    Discuss adding NAC with the clinician who prescribes your nitroglycerin.

    Discussion with the nitroglycerin prescriber; no dose, timing or self-adjustment instruction.

    Activated charcoal

    Source review required

    A spacing interval for routine oral NAC supplements has not been established. The reviewed absorption studies do not demonstrate clinical treatment failure.

    Activated charcoal may reduce absorption of oral acetylcysteine used in poisoning care. Small volunteer studies reported differing effects on absorption. This review does not establish a spacing rule for routine oral NAC supplements.

    If acetylcysteine is being used in poisoning care, follow the treating team's instructions for acetylcysteine and activated charcoal.

    Prescription oral acetylcysteine in poisoning care; not a supplement-spacing instruction.

    Anticoagulants

    Source review required

    The reviewed evidence does not establish the interaction risk for oral NAC with anticoagulants. It does not establish low clinical significance or a surgery stopping interval.

    This review does not establish how oral NAC affects bleeding risk when combined with anticoagulants. Intravenous and laboratory findings do not quantify the risk from routine oral supplements.

    This review has not established the interaction risk of routine oral NAC supplements with anticoagulants. Intravenous and laboratory findings do not establish a stopping interval before a procedure.

    View full N-Acetyl Cysteine (NAC) research page
    Green Tea Extract1 timing

    • Nadolol (beta-blocker)

      Green tea catechins reduce nadolol absorption via OATP inhibition. Reduced blood pressure control.

      ActionSeparate by 4 or more hours, or avoid.

    • Warfarin

      Small vitamin K content plus catechin antiplatelet effect. Unpredictable INR changes.

      ActionKeep intake consistent. Monitor INR.

    • Iron supplements

      Tannins in green tea chelate iron. Reduced iron absorption.

      ActionSeparate by 2 or more hours.

    • Stimulant medications (Adderall, Ritalin)

      Caffeine in green tea is additive. Excessive stimulation, anxiety, tachycardia.

      ActionLimit green tea on stimulant days.

    • MAOIs

      Caffeine plus tyramine interaction possible. Hypertensive crisis (rare).

      ActionAvoid high-caffeine green tea extracts on MAOIs.

    Timing Separation Rules

    • Nadolol4 hours
    View full Green Tea Extract research page
    Vitamin D

    Thiazide diuretics (HCTZ)

    • Vitamin D with Thiazide Diureticsmoderate

      Concurrent use of vitamin D and thiazide diuretics can lead to symptomatic hypercalcemia, which may present with nausea, vomiting, abdominal pain, muscle weakness, and altered mental status.

      Thiazide diuretics decrease urinary calcium excretion. When combined with vitamin D supplementation, which increases intestinal calcium absorption, the additive effect can result in elevated serum calcium levels (hypercalcemia).

      PMID 23307906

    ActionMonitor serum calcium.

    Steroids (prednisone)

    • Vitamin D with Prednisonecompatible

      Long-term glucocorticoids cause bone loss. Guidelines recommend calcium and vitamin D alongside them; take as advised. The guideline names glucocorticoids as a class; prednisone is the prototypical one.

      PMID 22885424

    • Orlistat (Alli)

      Reduces fat absorption, including fat-soluble vitamin D. Vitamin D deficiency.

      ActionSeparate by 2 or more hours. Monitor 25-OH vitamin D.

    • Cholestyramine (bile acid sequestrant)

      Reduces vitamin D absorption. Deficiency risk.

      ActionSeparate by 4 or more hours.
    View full Vitamin D research page
    Vitamin B6

    • Levodopa (without carbidopa)

      B6 increases peripheral conversion of levodopa to dopamine. Reduced efficacy (less dopamine reaches the brain).

      ActionVitamin B6 at 10 to 25 mg a day may reverse the effect of levodopa taken alone. Carbidopa blocks this effect, so it does not apply when levodopa is taken with carbidopa.

      SourceFDA label

    • Phenytoin (Dilantin)

      High-dose B6 may increase phenytoin metabolism. Reduced seizure control.

    View full Vitamin B6 research page
    Folic Acid

    Methotrexate

    • Folic Acid with Methotrexate

      Your prescriber may recommend this

      This medicine can lower your folate. Ask your prescriber whether you need it.

      Folic acid supplementation reduces the incidence of methotrexate-induced gastrointestinal and hepatic toxicity without significantly compromising its clinical efficacy in rheumatoid arthritis.

      Methotrexate is a folate antagonist that inhibits dihydrofolate reductase, leading to depletion of intracellular folate and subsequent inhibition of purine and pyrimidine synthesis. Folic acid supplementation replenishes folate stores, counteracting the toxic effects of methotrexate on healthy rapidly dividing cells.

      PMID 23728635

    • Folic Acid with Methotrexatecompatible

      Folic acid is routinely prescribed alongside methotrexate. In a double-blind placebo-controlled trial it did not reduce methotrexate's efficacy and lowered toxicity scores. Take it as prescribed.

      PMID 23728635

    Phenytoin (Dilantin)

    • Folic Acid with Phenytoinmoderate

      Ask your prescriber first

      Enzyme-inducing anti-seizure medicines lower folate and supplementation is routinely advised, especially before and during pregnancy. High-dose folic acid can lower phenytoin levels and reduce seizure control, so doses above the usual supplement range need monitoring.

      PMID 41560756

    • Folic Acid with Carbamazepine

      Your prescriber may recommend this

      This medicine can lower your folate. Ask your prescriber whether you need it.

      Enzyme-inducing anti-seizure medicines lower folate and supplementation is routinely advised, especially before and during pregnancy. Evidence is class-level for enzyme-inducing AEDs; the phenytoin-level-lowering caveat is phenytoin-specific and omitted here.

      PMID 41560756

    • 5-Fluorouracil (5-FU)

      Folic acid (as leucovorin) is sometimes given with 5-FU to enhance its effect. Increased toxicity and efficacy.

      ActionOnly under oncologist supervision.
    View full Folic Acid research page
    Garlic Supplementsstop before surgery

    Warfarin and other anticoagulants

    • Garlic high-dose extract with Warfarinmoderate

      Applies to concentrated garlic supplements and extracts, not to garlic eaten as food. The sources reviewed describe this risk by form rather than by a dose cutoff. Garlic supplements may add to the effect of blood thinners, so tell your surgeon or prescriber if you take them.

      Case reports of INR elevation and bleeding events on warfarin with high-dose garlic supplements. Culinary garlic intake unlikely to cause issue.

      High-dose garlic (allicin, ajoene) has antiplatelet effects via thromboxane synthesis inhibition. Some case reports also suggest CYP2C9 modulation affecting warfarin levels.

      PMID 21919844

    • Garlic with Anticoagulantsmoderate

      Concomitant use of garlic and anticoagulants may increase the risk of bleeding.

      Garlic contains compounds like ajoene and allicin that inhibit platelet aggregation and alter coagulation. This can enhance the pharmacological effect of anticoagulants.

      PMID 17918162

    • Garlic with Warfarinlow

      Controlled trials found no significant effect on INR. Bleeding case reports involving garlic did not involve patients taking warfarin.

      Garlic has theoretical antiplatelet activity.

      PMID 11144706

    ActionMonitor INR. Avoid high-dose garlic supplements on warfarin.

    HIV protease inhibitors (saquinavir)

    • Garlic with Saquinavircritical

      Do not combine

      Do not stop your medicine. Ask your prescriber before taking this supplement.

      PMID 11740713

    Blood pressure medications

    Applies to concentrated garlic supplements and extracts, not to garlic eaten as food. The sources reviewed describe this risk by form rather than by a dose cutoff. Garlic supplements may add to the effect of blood thinners, so tell your surgeon or prescriber if you take them.

    • Garlic high-dose extract with Metoprololmoderate

      Additive blood pressure lowering with Metoprolol. Monitor blood pressure when starting or stopping garlic supplements.

      High-dose garlic has documented blood pressure lowering effects via nitric oxide synthase modulation and H2S signaling.

      PMID 26764326

    • Garlic high-dose extract with Atenololmoderate

      Additive blood pressure lowering with Atenolol. Monitor blood pressure when starting or stopping garlic supplements.

      High-dose garlic has documented blood pressure lowering effects via nitric oxide synthase modulation and H2S signaling.

      PMID 26764326

    • Garlic high-dose extract with Bisoprololmoderate

      Additive blood pressure lowering with Bisoprolol. Monitor blood pressure when starting or stopping garlic supplements.

      High-dose garlic has documented blood pressure lowering effects via nitric oxide synthase modulation and H2S signaling.

      PMID 26764326

    Show 8 more
    • Garlic high-dose extract with Carvedilolmoderate

      Additive blood pressure lowering with Carvedilol. Monitor blood pressure when starting or stopping garlic supplements.

      High-dose garlic has documented blood pressure lowering effects via nitric oxide synthase modulation and H2S signaling.

      PMID 26764326

    • Garlic high-dose extract with Labetalolmoderate

      Additive blood pressure lowering with Labetalol. Monitor blood pressure when starting or stopping garlic supplements.

      High-dose garlic has documented blood pressure lowering effects via nitric oxide synthase modulation and H2S signaling.

      PMID 26764326

    • Garlic high-dose extract with Nebivololmoderate

      Additive blood pressure lowering with Nebivolol. Monitor blood pressure when starting or stopping garlic supplements.

      High-dose garlic has documented blood pressure lowering effects via nitric oxide synthase modulation and H2S signaling.

      PMID 26764326

    • Garlic high-dose extract with Propranololmoderate

      Additive blood pressure lowering with Propranolol. Monitor blood pressure when starting or stopping garlic supplements.

      High-dose garlic has documented blood pressure lowering effects via nitric oxide synthase modulation and H2S signaling.

      PMID 26764326

    • Garlic high-dose extract with Lisinoprillow

      Possible additive BP lowering. Generally minor; monitor blood pressure if starting high-dose garlic supplementation.

      High-dose garlic extract has mild antihypertensive effects via NO and vascular pathways. May be additive with Lisinopril.

    • Garlic high-dose extract with Enalaprillow

      Possible additive BP lowering. Generally minor; monitor blood pressure if starting high-dose garlic supplementation.

      High-dose garlic extract has mild antihypertensive effects via NO and vascular pathways. May be additive with Enalapril.

    • Garlic high-dose extract with Losartanlow

      Possible additive BP lowering. Generally minor; monitor blood pressure if starting high-dose garlic supplementation.

      High-dose garlic extract has mild antihypertensive effects via NO and vascular pathways. May be additive with Losartan.

    • Garlic high-dose extract with Telmisartanlow

      Possible additive BP lowering. Generally minor; monitor blood pressure if starting high-dose garlic supplementation.

      High-dose garlic extract has mild antihypertensive effects via NO and vascular pathways. May be additive with Telmisartan.

    ActionMonitor BP.

    • Isoniazid (TB treatment)

      Garlic may reduce isoniazid absorption. Treatment failure risk.

      ActionSeparate dosing.

    Stop 2 weeks before surgery

    Bleeding risk from antiplatelet effect.

    View full Garlic Supplements research page

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    Educational information only. Not medical advice. These statements have not been evaluated by the FDA. Talk to your prescriber before starting, stopping, or combining any supplement with prescription medication.