Melatonin
HormoneAlso known as: N-acetyl-5-methoxytryptamine
Melatonin is an endogenous hormone produced by the pineal gland in response to darkness, serving as the body's primary circadian timing signal. Unlike most supplements, melatonin is a hormone — a distinction with pharmacological and regulatory significance. Its strongest evidence base is in circadian rhythm disorders: jet lag, shift work disorder, and delayed sleep phase syndrome. Its role in improving sleep in otherwise healthy adults without circadian disruption is supported by evidence of modest effect size. A key evidence-informed insight is that commercial doses (5-10mg) are far above the physiological range, and lower doses (0.5mg) appear sufficient for circadian phase shifting with better tolerability. Timing of administration is at least as important as dose.
Evidence Summary
All 3 studiesMelatonin (N-acetyl-5-methoxytryptamine) is an endogenous hormone produced by the pineal gland in response to darkness, playing a central role in circadian rhythm regulation. Endogenous nocturnal melatonin secretion typically produces serum levels in the range of 100-200 pg/mL, peaking in the middle of the night. Commercial melatonin supplements are commonly sold in doses of 1-10mg — doses that produce serum levels orders of magnitude higher than physiological night-time peaks. This pharmacological reality is central to understanding the evidence base. The strongest evidence for melatonin supplementation is in circadian rhythm disorders. A systematic review (Brzezinski et al., 2007) found that melatonin taken at the appropriate local bedtime at the destination is effective in reducing jet lag symptoms and accelerating circadian resynchronization, particularly when crossing five or more time zones. Timing of administration is critical: melatonin administered at the wrong circadian phase can worsen circadian misalignment rather than improve it. The evidence for shift work disorder is similarly supported but less extensively reviewed. For primary sleep disorders in otherwise healthy adults, the evidence is more modest. A meta-analysis (Ferracioli-Oda et al., 2013, 19 studies) found that melatonin reduced sleep onset latency by a mean of approximately 7 minutes and increased total sleep time by approximately 8 minutes compared to placebo. These are statistically significant but clinically modest effects. Importantly, melatonin does not appear to substantially alter sleep architecture (deep sleep, REM proportion) — it functions primarily as a circadian timing signal rather than a sedative. Dose is a critical and frequently misunderstood variable. Research by Auger et al. (2018) and others supports the principle that 0.5mg can produce circadian phase advances comparable to higher doses, with fewer side effects. The common assumption that higher doses produce greater sleep benefits is not well-supported by evidence. Most experts now recommend starting with the lowest effective dose (0.5mg or below) before escalating. Long-term safety data is limited. Short-term use (weeks to months) appears well-tolerated in adults. Theoretical concerns exist about chronic high-dose supplementation suppressing endogenous melatonin production via feedback inhibition, though this has not been definitively demonstrated in controlled human trials. Melatonin is not recommended for children without medical supervision. Several drug interactions are relevant, particularly with anticoagulants, immunosuppressants, and hormonal contraceptives.
Read full evidence summary →Top studies
Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders
Melatonin significantly reduced sleep onset latency (mean 7.06 minutes), increased total sleep time (mean 8.25 minutes), and improved overall sleep quality compared to placebo. Effect sizes were modest but statistically significant. Effects were not as large as other sleep medications but the safety profile was favorable.
Melatonin may modestly reduce time to fall asleep and increase total sleep time in adults with primary sleep disorders
Generally well-tolerated in short-term trials; drowsiness and headache most commonly reported
High heterogeneity across included trials; variable doses (0.1mg to 10mg); variable study durations; limited data on long-term use; most studies relied on self-reported outcomes
Melatonin for the Prevention and Treatment of Jet Lag: A Systematic Review
Melatonin taken at the appropriate local bedtime at the destination is effective in reducing jet lag symptoms and accelerating circadian resynchronization, particularly when crossing five or more time zones. Timing of administration was identified as critically important — melatonin taken at the wrong circadian phase may worsen circadian disruption.
Melatonin is effective for reducing jet lag, particularly when crossing five or more time zones; timing relative to local destination time is the key variable
Generally well-tolerated for short-term jet lag use; taking at incorrect time may worsen circadian disruption
Variable doses across studies; jet lag is self-resolving; long-distance eastward travel more difficult than westward; blinding is challenging due to sedative effect
Expert Mentions
All 3 mentions"I want to be very clear about melatonin: most people are taking way too much. The doses in the pharmacy are 5, 10 milligrams — these are enormously supraphysiological. The actual amount your brain produces is probably in the range of 0.1 to 0.3 milligrams. If you're going to use melatonin, a dose of 0.5 milligrams is probably closer to what you want."
Most people take far too much melatonin. Commercial doses of 5-10mg are supraphysiological — the physiological range is closer to 0.1-0.5mg, and lower doses are likely more effective and associated with fewer next-day side effects.
Huberman's claim about supraphysiological commercial doses is well-supported. Endogenous nocturnal melatonin peaks are typically in the range of 100-200 pg/mL, and even low-dose supplementation (0.1-0.3mg) can produce serum levels that far exceed this. Research by Auger et al. and others supports that 0.5mg can produce circadian phase shifts comparable to higher doses with less residual sedation. This is one of Huberman's more evidence-aligned supplement claims.
"Melatonin is often misunderstood. People take it thinking it will knock them out or improve their deep sleep — but that's not really how it works. It's a circadian signal. It says, "it's time to sleep," but it doesn't particularly improve the quality of sleep once you're there. If you're using it for jet lag or shift work, that's where the evidence is strongest."
Melatonin is primarily a circadian timing signal, not a sleep-depth enhancer. It tells the brain when to sleep but does not meaningfully improve deep sleep or sleep architecture in the way that other interventions (e.g., behavioral or pharmacological) do.
Attia's framing is accurate and well-supported by the literature. Meta-analyses (Ferracioli-Oda et al., 2013) show modest reductions in sleep onset latency but minimal effects on slow-wave or REM sleep architecture. The strongest evidence is for circadian rhythm disorders (jet lag, shift work, delayed sleep phase) rather than general sleep quality improvement in healthy adults. This represents an accurate and appropriately nuanced characterization of the melatonin evidence.
Key findings
- ·Strongest evidence is for jet lag: melatonin taken at destination local bedtime accelerates circadian resynchronization, especially when crossing 5+ time zones.
- ·For primary sleep disorders, melatonin modestly reduces sleep onset latency (~7 min) and increases total sleep time (~8 min) versus placebo — effect sizes are real but small.
- ·Melatonin is a circadian timing signal, not a sleep architecture enhancer — effects on deep sleep or REM are minimal.
Evidence gaps
- ·Long-term safety data (beyond several months of continuous use) in adults is lacking.
- ·Whether chronic high-dose use suppresses endogenous melatonin production has not been definitively tested in controlled human trials.
- ·Effects in healthy adults without circadian disruption or sleep disorders are poorly defined.