Melatonin Reference

Plain English

What it is

Melatonin is a hormone your brain makes in response to darkness that helps set your body's daily sleep clock. In the United States it is sold over the counter as a dietary supplement, not as an FDA-approved drug, so it is checked less strictly than a real medicine.

What people use it for

People in the sleep and jet-lag communities often reach for it first to fall asleep a little faster or to reset their body clock after travel or a shifted sleep schedule.

What the science shows

Studies that pool many trials find it makes a small but real difference in how fast people fall asleep. The evidence looks stronger for sleep-timing problems like jet lag and delayed sleep phase than for ordinary long-term insomnia, where major guidelines say there is not enough strong evidence to recommend it.

The catch

Because it is sold as a supplement rather than a regulated drug, the amount in the bottle can vary widely from what the label claims, and some products have been found to contain serotonin, another hormone that can be harmful even at low levels. In many other countries melatonin is available only with a prescription.

Reference summary

Two widely cited meta-analyses (Ferracioli-Oda 2013 PLoS One; Auld 2017 Sleep Med Rev) report small but consistent reductions in sleep-onset latency and modest gains in total sleep time in primary insomnia. The effect is larger for circadian-phase shifting (jet lag, delayed sleep phase) than for primary insomnia. NIH Office of Dietary Supplements maintains a health-professional fact sheet summarizing the evidence and safety profile.

Regulatory and posture

Categories

Sleep, Longevity

Aliases

N-acetyl-5-methoxytryptamine, Pineal hormone analog (OTC dietary supplement in the US)

Evidence posture

human - Small effect size on sleep onset; meta-analyses are heterogeneous. Supplement-content variability is well documented.

Regulatory status

Over-the-counter dietary supplement in the United States; prescription-only in many other countries (United Kingdom, European Union, Australia, Canada for most adult use). Not FDA-approved as a drug; oral melatonin supplements are regulated under DSHEA, which means label content can vary substantially from analytical content (Erland 2017 J Clin Sleep Med).

Content review status

research reference