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Endogenous pineal hormone that signals biological night and advances the sleep-wake (circadian) phase via MT1/MT2 receptors.
The best-supported sleep active. A meta-analysis of 19 RCTs (1,683 subjects) found melatonin significantly reduced sleep onset latency by ~7.1 minutes, increased total sleep time by ~8.3 minutes, and modestly improved sleep quality (SMD 0.22) versus placebo. Effects are real but smaller than prescription hypnotics, and the side-effect profile is benign. Strongest for circadian/delayed-phase and shift problems; benefit for chronic insomnia is modest.
0.5-5 mg taken ~30 min to 3 h before bedtime; dose-response data suggest efficacy peaks around 4 mg, but lower doses (0.5-1 mg) are often sufficient and more physiologic.
Educational summary of doses studied — not a recommendation. Talk to a clinician before starting any supplement.
Educational summary of published research, checked against primary sources and linked inline. Not medical advice; supplements are not FDA-evaluated to treat disease. See our editorial policy.