Find the research-backed melatonin dose and exact timing for your specific goal. Most OTC products contain 10–20× too much — here's what the science actually says.
Melatonin is one of the most misunderstood supplements in common use. Despite being marketed primarily as a sleep aid — and despite OTC products typically containing 5–10mg doses — melatonin is not a sedative. It doesn't cause drowsiness or directly induce sleep. It is a circadian signal — a hormone that tells your body clock that it's nighttime. Understanding this distinction is crucial for using melatonin correctly.
Melatonin is produced by the pineal gland in response to darkness. As light fades in the evening, the suprachiasmatic nucleus (SCN) — your master circadian clock — releases the inhibition on the pineal gland, allowing melatonin synthesis and secretion. Melatonin levels rise approximately 2 hours before your habitual sleep time, peak around midnight, and fall again toward morning.
Melatonin receptors are located in the SCN itself and throughout the body. When melatonin binds to SCN receptors, it reinforces the clock's "nighttime" state and helps synchronize peripheral clocks in other organs. This is the mechanism by which melatonin exogenously administered (as a supplement) can shift the circadian clock — not by sedating you, but by providing a "darkness" signal to the SCN.
Critically, this clock-shifting effect is dose-dependent in the wrong direction: higher doses don't shift the clock more effectively. The SCN's melatonin receptors saturate at very low concentrations — approximately 0.1–0.3mg produces near-maximal receptor occupancy. Doses above this produce pharmacological (above-physiological) levels that can actually reduce receptor sensitivity through desensitization over time.
The research-validated effective dose of melatonin for circadian shifting is 0.3–0.5mg. This was established in landmark studies by Richard Wurtman et al. at MIT in the 1990s, which systematically compared doses from 0.1mg to 10mg. The 0.3mg and 0.5mg doses produced equivalent or superior clock-shifting effects compared to 1–10mg doses, while producing physiological (not pharmacological) blood levels.
Despite this well-established research, the supplements industry has marketed products at doses 10–20× higher than the evidence supports. Why? Partly because higher doses feel more sedating (through non-specific sedating effects at pharmacological levels), making consumers feel they're getting a stronger sleep effect. But "feeling sleepy" is not the same as "circadian clock is advancing optimally." High-dose melatonin may impair the very clock-shifting it's intended to produce.
Jet lag: Melatonin has the strongest evidence base for jet lag specifically, with multiple RCTs showing it accelerates circadian adaptation. The Cochrane review by Herxheimer and Petrie (2002) found melatonin effective for jet lag at doses of 0.5–5mg taken at destination bedtime. Timing is critical — taken at the wrong time, melatonin can worsen jet lag by shifting the clock in the wrong direction.
Delayed Sleep Phase Syndrome (DSPS): People who cannot fall asleep until 2–4 AM regardless of effort have a phase-delayed circadian clock. Melatonin taken 5–6 hours before the natural sleep time (combined with morning bright light) can gradually advance the clock over weeks. This requires consistency — it takes 2–4 weeks of nightly use to shift the clock meaningfully.
General insomnia: For insomnia not related to circadian timing, melatonin has only modest efficacy. The average sleep onset reduction is approximately 7 minutes — statistically significant but clinically modest. CBT-I is dramatically more effective for non-circadian insomnia.
Shift work: Strategic melatonin use can help shift workers adapt to day sleeping. Taken immediately before the desired sleep time (for day shifts), it can improve daytime sleep quality. However, shifting workers between night and day schedules with melatonin requires careful timing and is best done with guidance.