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Increases INR/bleeding risk
Monitor INR closely if combining.
Additive sedation
Use caution, especially when driving next day.
Reduces melatonin levels
May need higher dose.
Increases melatonin levels
Use lower dose.
Reduces melatonin levels
Smokers may need higher doses.
Significantly increases melatonin
Reduce melatonin dose significantly.
Reduces drug effectiveness
Monitor BP.
Increases melatonin levels
Avoid caffeine close to bedtime regardless.
Unclear effect on clotting
Monitor if on anticoagulants.
Possible glucose effects
Monitor blood glucose if diabetic.
Additive nighttime BP reduction
Monitor. Usually benign.
Major issue. Canadian study: only 9 of 31 tested supplements were within 10% of labeled melatonin. Content ranged from 83% less to 478% more. 8 supplements contained serotonin (undeclared). This is a serious quality control problem.
Not Prohibited.
Major issue. Canadian study: only 9 of 31 tested supplements were within 10% of labeled melatonin. Content ranged from 83% less to 478% more. 8 supplements contained serotonin (undeclared). This is a serious quality control problem.
Reference identifiers on this page are being re-verified against PubMed. Some may not yet link to the paper named beside them.
**, Li T et al. "Exogenous melatonin as a treatment for secondary sleep disorders: A systematic review and meta-analysis." *Front Neuroendocrinol*, 2019. Key finding: Melatonin improved sleep quality in secondary sleep disorders (medical conditions causing insomnia).
Exogenous melatonin as a treatment for secondary sleep disorders: A systematic review and meta-analysis.. (2019). PMID: 30215696
**, Erland LA et al. "Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content." *J Clin Sleep Med*, 2017. Key finding: 71% of tested melatonin supplements did not meet label claims (±10%). Serotonin contamination found in 26%.
Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content.. (2017). PMID: 28460563
**, Auld F et al. "Evidence for the efficacy of melatonin in the treatment of primary adult sleep disorders." *Sleep Med Rev*, 2017. Key finding: Melatonin improves sleep onset latency and total sleep time in primary insomnia.
Evidence for the efficacy of melatonin in the treatment of primary adult sleep disorders.. (2017). PMID: 31722088
Based on independent third-party laboratory analysis
Category pass rate: ~85% pass rate. Primary issue: massive dose variation (up to 478% between highest/lowest variance products). Gummies tend to have higher variance than pills.
Melatonin reduces time to fall asleep by 12-17 minutes only (not hours); Does NOT improve sleep quality or total sleep time; Lower doses (0.3-1mg) are as effective as higher doses for sleep onset; Higher doses are NOT more effective — they just increase side effects
Independently graded against 173,636 indexed supplements with 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated: April 5, 2026
Not medical advice. Based on published clinical research and systematic reviews.
Melatonin · interaction landscape
5 flagged
0
Dangerous
5
Moderate
0
Timing
0
Pre-op
Safety
Moderate interactions. Monitoring, timing separation, or dose adjustment may be required.
Warfarin and other anticoagulants
SourceCase reports
Immunosuppressants
SourceClinical pharmacology
Diabetes medications
SourceClinical consensus
Sedatives and benzodiazepines
SourceClinical consensus
Fluvoxamine (Luvox)
SourceClinical pharmacology
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.