Melatonin is the most popular sleep aid in the United States, sold over the counter, taken by millions, and widely misunderstood. It is not a sedative. It does not put you to sleep the way a benzodiazepine does. It is a timing signal, and it works well for the narrow set of problems it was designed to address and poorly for most of what people take it for.
Understanding the difference between a chronobiotic and a hypnotic is the whole game.
What melatonin actually does
Melatonin is a hormone produced by the pineal gland in response to darkness. Its release, starting a couple of hours before your natural bedtime, is the brain's internal cue that biological night has begun. Body temperature drops, alertness declines, and the machinery of sleep starts up.
Supplemental melatonin, taken at the right time, can nudge that internal clock earlier or later. This is called a phase shift, and it is the mechanism behind melatonin's real, evidence-supported uses.
- Jet lag, especially eastward travel across multiple time zones
- Delayed sleep-wake phase disorder, where the natural sleep window is shifted late
- Shift work, in some protocols under clinical guidance
- Some sleep problems in children with neurodevelopmental conditions, under medical supervision
For ordinary adult insomnia, particularly the "I can't fall asleep because my mind is racing" kind, melatonin's effect is modest at best. The AASM's clinical practice guidance does not recommend melatonin as a first-line treatment for chronic insomnia in adults.
Dose and timing matter more than most people realize
Over-the-counter melatonin in the US is often sold in 3, 5, or 10 milligram doses. These are pharmacological doses, many multiples of what the pineal gland releases. The most effective doses for phase-shifting are far smaller, typically 0.3 to 0.5 milligrams, taken several hours before the target bedtime, not right before bed.
High doses can produce next-day grogginess and vivid dreams, and they may actually work less well than low doses for circadian shifting because they saturate receptors.
More is not stronger. It is often just messier.
The quality problem
Melatonin is regulated as a dietary supplement in the US, which means less rigorous oversight of what is actually in the bottle. Independent analyses have repeatedly found that the melatonin content of over-the-counter products can vary substantially from the label, sometimes containing far more or far less than stated, and occasionally containing contaminants such as serotonin.
Look for products with a USP Verified mark or equivalent third-party testing. This does not guarantee efficacy, but it makes label accuracy far more likely.
Melatonin in children
Pediatric melatonin use has risen sharply, and so have accidental ingestions reported to poison control centers, mostly involving gummies mistaken for candy. Melatonin is not approved by the FDA for pediatric use, and the American Academy of Pediatrics urges parents to consult a clinician before giving it to a child. Short-term use for specific sleep-onset problems in some children has evidence behind it. Casual, nightly use as a bedtime routine does not.
When it is worth trying, and when it is not
Melatonin is reasonable to try for jet lag: a small dose (0.5-1 mg) taken at the target bedtime in the new time zone, for a few days, alongside morning light exposure. It is reasonable to try for a naturally late sleep schedule you are trying to shift earlier, taken several hours before your desired bedtime.
It is not the right tool for stress-driven insomnia, for sleep-maintenance insomnia (waking at 3 AM), or for sleep problems caused by an unaddressed medical issue like sleep apnea. For chronic insomnia, cognitive behavioral therapy for insomnia (CBT-I) has stronger evidence than any pill.
The bottom line
Melatonin is a clock-setter, not a knockout drop. Used at low doses and correct timing for the right problems, jet lag, phase shifts, it works. Used nightly at high doses for generic insomnia, it mostly buys you a placebo and a supplement industry markup, and it can be genuinely risky in children when treated like candy.