What is the recommended dose of Calcium?

- **Total daily calcium (food + supplement):** 1,000-1,200mg/day - **Supplement dose:** ≤500mg per dose (absorption saturates above 500mg) - **Split doses** at least 4 hours apart - **ALWAYS co-sup...

Is Calcium safe to take daily?

Calcium is rated "Prescription Interactions" based on clinical evidence. Always consult your healthcare provider before starting any supplement.

Does Calcium interact with any medications?

Calcium has 8 known drug interactions, including interactions with Levothyroxine (Synthroid), Fluoroquinolone antibiotics (cipro), Tetracycline antibiotics. Check with your doctor before combining with prescription medications.

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Ingredient Research

Graded against 173,636 supplements + 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, NIH DSLD

Calcium

STRONG EVIDENCEMineralLast updated April 2026

AVELOR SUMMARY

Calcium is the most abundant mineral in the human body, 99% stored in bones and teeth. Our research confirms supplementation prevents bone loss in postmenopausal women but raises legitimate cardiovascular concerns at doses above 1,000mg/day from supplements. The form matters (citrate > carbonate for absorption), timing matters (never with thyroid medication), and the cardiovascular risk signal means food-based calcium is preferred over pills when possible.

EVIDENCE GRADES

Bone mineral density (postmenopausal)Strong, Cochrane review (UNCITED: the cited PMID did not support this claim and was removed; this statement is not currently sourced)

Fracture prevention (with vitamin D)Strong when combined with D

B+

Blood pressure reductionModest effect in hypertensive populations

B-

Colorectal cancer preventionModerate, large observational data

B-

Cardiovascular riskMeta-analyses show possible 20-30% increased MI risk with supplements >1,000mg/day (PMID: 21505219)

⚠️ CONCERN

WHAT IT DOES

Calcium is essential for bone mineralization, muscle contraction, nerve transmission, blood clotting, and enzyme function. Bone constantly remodels, osteoblasts build, osteoclasts resorb. After menopause, resorption outpaces formation, leading to osteoporosis. Calcium supplementation + vitamin D slows this imbalance.

Supplemental forms differ:

Calcium carbonate: 40% elemental calcium, requires stomach acid for absorption. Take with food. Cheapest.
Calcium citrate: 21% elemental calcium, absorbed independent of stomach acid. Take anytime. Better for PPI users and older adults.
Calcium phosphate, lactate, gluconate: Lower elemental calcium percentages. Less commonly used.
Hydroxyapatite: Bone-derived form with accompanying phosphorus and trace minerals. Theoretical advantage for bone health.

OPTIMAL DOSAGE

Total daily calcium (food + supplement): 1,000-1,200mg/day
Supplement dose: ≤500mg per dose (absorption saturates above 500mg)
Split doses at least 4 hours apart
ALWAYS co-supplement with vitamin D (1,000-4,000 IU) and consider K2 (100-200mcg MK-7) to direct calcium to bones, not arteries

Scan a supplement containing Calcium

DRUG INTERACTIONS

Levothyroxine (Synthroid)Severe

Chelation, reduces thyroid hormone absorption by up to 60%. Separate by ≥4 HOURS.

Fluoroquinolone antibiotics (cipro)Severe

Chelation, reduces antibiotic absorption. Separate by ≥2 hours.

Tetracycline antibioticsSevere

Chelation. Separate by ≥2 hours.

Bisphosphonates (alendronate)Severe

Chelation. Separate by ≥2 hours.

Iron supplementsModerate

Competitive absorption. Separate by ≥2 hours.

Thiazide diureticsModerate

Reduce calcium excretion + calcium supplementation → hypercalcemia risk

DigoxinModerate

Hypercalcemia increases digoxin toxicity risk

ZincModerate

Competitive absorption at high doses

SAFETY PROFILE

Drug Interactions

⚠️ Cardiovascular Concern

A 2011 meta-analysis of 11 RCTs found calcium supplements (without co-administered vitamin D) increased myocardial infarction risk by approximately 27% (PMID: 21505219). The proposed mechanism: calcium supplements cause acute spikes in serum calcium that may accelerate vascular calcification. This risk signal is NOT seen with dietary calcium.

Our recommendation: Get calcium primarily from food. If supplementing, keep supplement dose ≤500mg/day, always co-administer vitamin D + K2, and prefer calcium citrate.

Pregnancy & Lactation

Recommended during pregnancy (1,000-1,300mg/day total). WHO recommends calcium supplementation in populations with low dietary calcium intake to reduce preeclampsia risk.

WADA Status

Not Prohibited

HOW AVELOR SCORES THIS

Products >1,000mg calcium per serving: flag cardiovascular concern

Products without vitamin D co-formulation: recommend adding D + K2

Calcium carbonate in products for PPI users: flag, they need citrate form

Levothyroxine/antibiotic users: automatic 4-hour/2-hour separation alert

≤500mg per dose maximum: flag products exceeding this

Hydroxyapatite form: score minor bonus for bone health applications

CLINICAL REFERENCES

Reference identifiers on this page are being re-verified against PubMed. Some may not yet link to the paper named beside them.

, Bolland MJ et al. Calcium supplements with or without vitamin D and risk of cardiovascular events.

PMID: 21505219

, Heaney RP. Calcium supplementation and incident kidney stone risk.

PMID: 17720017

RELATED RESEARCH

BoronBoron influences the metabolism of calcium, magnesium, phosphorus, and vitamin D

Calcium AEP**The entire direct human literature on calcium AEP located in PubMed is three clinical reports from

Calcium D-GlucarateIn the rat DMBA mammary carcinogenesis model, dietary calcium D-glucarate fed after carcinogen expos

Chromium

Scan Your Calcium Supplement Browse all ingredients

Independently graded against 173,636 indexed supplements with 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated: April 2026

Not medical advice. Based on published clinical research and systematic reviews.

Calcium · interaction landscape

9 flagged

Dangerous

Moderate

Timing

Pre-op

Safety

Calcium: Drug Interactions

Use with caution

Moderate interactions. Monitoring, timing separation, or dose adjustment may be required.

Levothyroxine (Synthroid)
Calcium binds levothyroxine in the gut.
RiskSubtherapeutic thyroid hormone. Hypothyroid symptoms may return.
ActionSeparate by 4 or more hours.
SourceFDA label
Tetracycline and doxycycline
Calcium chelates the antibiotic.
RiskAntibiotic treatment failure.
ActionSeparate by 2 to 3 hours.
SourceFDA label
Fluoroquinolones (Cipro)
Calcium chelates the antibiotic.
RiskAntibiotic treatment failure.
ActionTake 2+ hours before or 6+ hours after the antibiotic.
SourceFDA label
Iron supplements
Calcium blocks iron absorption.
RiskIron deficiency.
ActionTake at different meals.
SourceClinical consensus
Bisphosphonates (Fosamax)
Calcium blocks bisphosphonate absorption.
RiskReduced bone drug efficacy.
ActionTake bisphosphonate on an empty stomach; calcium later.
SourceFDA label
Thiazide diuretics (HCTZ)
Both increase serum calcium.
RiskHypercalcemia.
ActionMonitor calcium levels.
SourceClinical pharmacology

Timing Separation Rules

Levothyroxine4 hours
Tetracycline / fluoroquinolone antibiotics2 to 3 hours
Bisphosphonates2+ hours after bisphosphonate

Educational information only. This is 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.

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Ingredient Research

Graded against 173,636 supplements + 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, NIH DSLD

Calcium

STRONG EVIDENCEMineralLast updated April 2026

AVELOR SUMMARY

EVIDENCE GRADES

Bone mineral density (postmenopausal)Strong, Cochrane review (UNCITED: the cited PMID did not support this claim and was removed; this statement is not currently sourced)

Fracture prevention (with vitamin D)Strong when combined with D

B+

Blood pressure reductionModest effect in hypertensive populations

B-

Colorectal cancer preventionModerate, large observational data

B-

Cardiovascular riskMeta-analyses show possible 20-30% increased MI risk with supplements >1,000mg/day (PMID: 21505219)

⚠️ CONCERN

WHAT IT DOES

Supplemental forms differ:

Calcium carbonate: 40% elemental calcium, requires stomach acid for absorption. Take with food. Cheapest.
Calcium citrate: 21% elemental calcium, absorbed independent of stomach acid. Take anytime. Better for PPI users and older adults.
Calcium phosphate, lactate, gluconate: Lower elemental calcium percentages. Less commonly used.
Hydroxyapatite: Bone-derived form with accompanying phosphorus and trace minerals. Theoretical advantage for bone health.

OPTIMAL DOSAGE

Total daily calcium (food + supplement): 1,000-1,200mg/day
Supplement dose: ≤500mg per dose (absorption saturates above 500mg)
Split doses at least 4 hours apart
ALWAYS co-supplement with vitamin D (1,000-4,000 IU) and consider K2 (100-200mcg MK-7) to direct calcium to bones, not arteries

Scan a supplement containing Calcium

DRUG INTERACTIONS

Levothyroxine (Synthroid)Severe

Chelation, reduces thyroid hormone absorption by up to 60%. Separate by ≥4 HOURS.

Fluoroquinolone antibiotics (cipro)Severe

Chelation, reduces antibiotic absorption. Separate by ≥2 hours.

Tetracycline antibioticsSevere

Chelation. Separate by ≥2 hours.

Bisphosphonates (alendronate)Severe

Chelation. Separate by ≥2 hours.

Iron supplementsModerate

Competitive absorption. Separate by ≥2 hours.

Thiazide diureticsModerate

Reduce calcium excretion + calcium supplementation → hypercalcemia risk

DigoxinModerate

Hypercalcemia increases digoxin toxicity risk

ZincModerate

Competitive absorption at high doses

SAFETY PROFILE

Drug Interactions

⚠️ Cardiovascular Concern

Our recommendation: Get calcium primarily from food. If supplementing, keep supplement dose ≤500mg/day, always co-administer vitamin D + K2, and prefer calcium citrate.

Pregnancy & Lactation

Recommended during pregnancy (1,000-1,300mg/day total). WHO recommends calcium supplementation in populations with low dietary calcium intake to reduce preeclampsia risk.

WADA Status

Not Prohibited

HOW AVELOR SCORES THIS

Products >1,000mg calcium per serving: flag cardiovascular concern

Products without vitamin D co-formulation: recommend adding D + K2

Calcium carbonate in products for PPI users: flag, they need citrate form

Levothyroxine/antibiotic users: automatic 4-hour/2-hour separation alert

≤500mg per dose maximum: flag products exceeding this

Hydroxyapatite form: score minor bonus for bone health applications

CLINICAL REFERENCES

Reference identifiers on this page are being re-verified against PubMed. Some may not yet link to the paper named beside them.

, Bolland MJ et al. Calcium supplements with or without vitamin D and risk of cardiovascular events.

PMID: 21505219

, Heaney RP. Calcium supplementation and incident kidney stone risk.

PMID: 17720017

RELATED RESEARCH

BoronBoron influences the metabolism of calcium, magnesium, phosphorus, and vitamin D

Calcium AEP**The entire direct human literature on calcium AEP located in PubMed is three clinical reports from

Calcium D-GlucarateIn the rat DMBA mammary carcinogenesis model, dietary calcium D-glucarate fed after carcinogen expos

Chromium

Scan Your Calcium Supplement Browse all ingredients

Independently graded against 173,636 indexed supplements with 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated: April 2026

Not medical advice. Based on published clinical research and systematic reviews.

Calcium · interaction landscape

9 flagged

Dangerous

Moderate

Timing

Pre-op

Safety

Calcium: Drug Interactions

Use with caution

Moderate interactions. Monitoring, timing separation, or dose adjustment may be required.

Levothyroxine (Synthroid)
Calcium binds levothyroxine in the gut.
RiskSubtherapeutic thyroid hormone. Hypothyroid symptoms may return.
ActionSeparate by 4 or more hours.
SourceFDA label
Tetracycline and doxycycline
Calcium chelates the antibiotic.
RiskAntibiotic treatment failure.
ActionSeparate by 2 to 3 hours.
SourceFDA label
Fluoroquinolones (Cipro)
Calcium chelates the antibiotic.
RiskAntibiotic treatment failure.
ActionTake 2+ hours before or 6+ hours after the antibiotic.
SourceFDA label
Iron supplements
Calcium blocks iron absorption.
RiskIron deficiency.
ActionTake at different meals.
SourceClinical consensus
Bisphosphonates (Fosamax)
Calcium blocks bisphosphonate absorption.
RiskReduced bone drug efficacy.
ActionTake bisphosphonate on an empty stomach; calcium later.
SourceFDA label
Thiazide diuretics (HCTZ)
Both increase serum calcium.
RiskHypercalcemia.
ActionMonitor calcium levels.
SourceClinical pharmacology

Timing Separation Rules

Levothyroxine4 hours
Tetracycline / fluoroquinolone antibiotics2 to 3 hours
Bisphosphonates2+ hours after bisphosphonate

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Explore

Browse All 834 Ingredients Browse All 20 Conditions