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Published 2025-12-23 · Last reviewed 2025-12-30 · 5 references
Content sourced from FDA labeling (DailyMed) and peer-reviewed literature.
Melatonin is an endogenous hormone that helps regulate circadian sleep-wake timing. In the United States it is commonly used as an OTC dietary supplement (not FDA-approved as a drug).
It is often used for sleep-onset insomnia and circadian rhythm complaints (e.g., delayed sleep timing, jet lag). In insomnia studies, effect sizes are usually modest; meta-analyses suggest small average improvements in sleep latency and total sleep time versus placebo.
The AASM guideline recommends against routine melatonin use for chronic insomnia in adults (weak recommendation), so treat it as a time-limited adjunct and prioritize CBT-I and treatment of comorbid drivers (mood episodes, substances, pain, sleep apnea, circadian disruption).
A practical safety issue is supplement variability: analyses of OTC products have found large differences between labeled and measured melatonin content, and some products contain serotonin (Erland 2017).
The melatonin compare view, evidence feed, and print page support side-by-side review with prescription alternatives.
Melatonin is widely used because it is accessible, inexpensive, and not a controlled substance. However, OTC supplement variability is a meaningful quality and dosing issue; consider reputable manufacturers and avoid stacking multiple melatonin products.
View labelExactRefer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.
Melatonin binds MT1 and MT2 receptors, supporting circadian timing and sleep onset by modulating wake-promoting signals.
It is not a GABAergic sedative-hypnotic, so it generally does not produce “knockout” sedation; it works best when sleep-onset difficulty and circadian misalignment are key drivers.
Timing is a core part of the intervention: taking melatonin too late can increase morning sleepiness and reduce usefulness (clinical).