Melatonin is a hormone produced by the pineal gland that signals darkness to the body and sets circadian phase. As a supplement it is most effective for circadian disruptions — jet lag, shift work, delayed sleep phase — not as a sedative for general insomnia. Most people take far too much of it.
Melatonin is the clearest tool for circadian rhythm disruption. For general sleep difficulty it is more modest. The ideal dose is far lower than what most products contain — 0.5 mg often works as well as 5 mg with fewer side effects.
Each row grades the claimed effect by strength of human evidence, not mechanism or marketing.
Effective for circadian phase disruption. A reasonable short-term option for jet lag and shift work. Not a first-line treatment for chronic insomnia.
Often used nightly in high doses as a general sleep supplement; sometimes promoted for anti-aging and immune support.
The dose gap is the most important misunderstanding. Standard OTC doses (3–10 mg) are pharmacological, not physiological. Most research showing benefit used 0.5–1 mg. Higher doses may produce next-day grogginess, and long-term nightly safety data remain limited.
Melatonin is a phase-shifting signal, not a sleep drug — it tells the body when to sleep, not how to sleep.
The most robust evidence is for jet lag, particularly eastward travel, where 0.5–5 mg taken at destination bedtime shortens adaptation.
Effective dose is much lower than common product doses — 0.5 mg is often indistinguishable from 3 mg in RCTs.
Long-term nightly use has not been shown to damage natural melatonin production in short studies, but long-term data are limited.
US supplement products may contain substantially more or less melatonin than the label states; quality control matters.
Timing matters more than dose — taking melatonin at the wrong phase can actually delay sleep.
Mechanism is not outcome. Each mechanism is labelled by how far it has been validated in humans.
Melatonin acts on MT1 and MT2 receptors in the suprachiasmatic nucleus (the brain's master clock), signalling darkness and suppressing wake-promoting activity.
Taken at the right time relative to current circadian phase, melatonin can advance or delay the body clock — the core mechanism for jet lag treatment.
Melatonin promotes peripheral vasodilation and modest core temperature reduction, facilitating the thermal conditions for sleep onset.
Melatonin is a potent free radical scavenger in cell studies. Whether supplemental doses confer meaningful antioxidant protection in humans is unclear.
Short-term use at low doses is well-tolerated in healthy adults. Long-term nightly use is less studied. Unlike most sleep medications, no dependence or withdrawal syndrome has been documented.
This page is educational and not medical advice. Melatonin is a hormone. Use in children, pregnant women and people on medications should be discussed with a clinician.
A small, curated set — not a literature dump. Each reference comes with a single-line takeaway.
Melatonin is effective for preventing or reducing jet lag. Doses of 0.5–5 mg are similarly effective; higher doses may cause more side effects.
Melatonin reduced sleep onset latency and increased total sleep time in primary sleep disorders, though effect sizes were modest.
0.3 mg melatonin increased sleepiness and lowered core body temperature at the correct circadian time — confirming low-dose efficacy.