Melatonin: Benefits, Dosage, and What the Research Says

Melatonin is a hormone your body makes in the pineal gland when it gets dark. It is the signal that tells your brain "it is nighttime," which is why light at night suppresses it and darkness raises it. It does not knock you out like a sleeping pill; it shifts the timing of your sleep-wake cycle.

As a supplement, melatonin is used to reinforce that night-time signal, most usefully when your internal clock is out of sync with the clock on the wall (jet lag, a night-owl schedule, shift work). Understanding it as a timing cue rather than a sedative is the key to using it well, and it explains why the dose and, especially, the timing matter so much.

Melatonin acts on two receptors (MT1 and MT2) that are involved in setting your circadian clock. At low doses, it works as a "chronobiotic," gently shifting the timing of your body's own melatonin rise. At high doses, it stops adding clock-shifting benefit and instead just floods the system, which is where the extra side effects come from without extra results.⁹

This is why the research keeps landing on the same practical rule: take a small amount, and take it at the right time. A dose-response analysis of 26 trials found the sweet spot was around a few milligrams, taken well before your target bedtime, with diminishing returns above that.⁷

What the research shows

A meta-analysis of 19 randomized trials (1,683 people) found melatonin shortened the time to fall asleep by about 7 minutes, added roughly 8 minutes of total sleep, and modestly improved sleep quality versus placebo.¹ A larger 2022 meta-analysis of 23 trials found a significant improvement in overall sleep-quality scores.⁵

These are genuine, repeatable effects, but they are modest compared to prescription sleep medications, and they are strongest for helping you drift off rather than keeping you asleep all night. For occasional trouble winding down, melatonin is a reasonable, low-key option, not a heavy hitter.

Melatonin's clearest win is jet lag. A Cochrane review of 10 trials found it effective when taken near bedtime at your destination after crossing five or more time zones, with a number-needed-to-treat of 2 (meaning it helped roughly one in every two travelers).² Crucially, that same review found doses above 5 mg gave no extra benefit.

It also helps people whose body clock runs late (the classic "night owl" who cannot fall asleep until the early hours). A meta-analysis found melatonin advanced sleep onset by around 40 minutes and shifted the body's own melatonin rise by over an hour, and the authors specifically concluded the dose should be kept as low as possible.³ For shift workers, the evidence is weaker: melatonin modestly extended daytime sleep after a night shift (about 24 minutes) but the quality of evidence was low.⁶

This is the most important and most misunderstood part of melatonin. Because it is sold in everything from 0.5 mg up to 60 mg, people assume a bigger number means a stronger effect. The research says the opposite.

Your body's own nightly melatonin output is tiny, roughly equivalent to a fraction of a milligram. A dose of just 0.5 mg already pushes blood levels well above normal.⁹ The dose-response evidence points to an optimal effect around a few milligrams, with diminishing returns above that,⁷ the Cochrane jet-lag review found no added benefit past 5 mg,² and a safety review of 79 trials found doses of 10 mg or more significantly increased side effects like drowsiness, headache, and dizziness.⁸

The honest bottom line: start at the lowest dose (0.5 to 3 mg) and focus on timing. Higher-strength products exist, but for most people they are more likely to cause next-day grogginess than better sleep. See the dosing table below.