Melatonin

Discovery of the hormone

A 2017 pharmacology review by Tordjman and colleagues states that melatonin was discovered and isolated from bovine pineal tissue in 1958 by Aaron Lerner. The review describes pineal cells making melatonin from tryptophan by way of serotonin, with synthesis enhanced by darkness and inhibited by light, and light information reaching the pineal gland from the retina through the suprachiasmatic nucleus. It reports that nearly 80% of production occurs at night, with secretion peaking around 2 to 4 a.m.

The same review characterizes melatonin as an endogenous synchronizer and chronobiotic, acting through MT1 and MT2 receptors. The sources reviewed for this page do not provide a dated account of how isolated melatonin became a popular supplement in the 1990s, or of the role of individual researchers such as Richard Wurtman in that period, so this page does not assert one.

From hormone to supplement and medicine

In the United States, synthetic melatonin products are widely available over the counter and are regulated by the Food and Drug Administration as dietary supplements. A 2022 CDC report cites sales rising from $285 million in 2016 to $821 million in 2020. The National Center for Complementary and Integrative Health (NCCIH) notes that in several other countries melatonin requires a prescription, and the NHS lists licensed melatonin medicines under brand names including Circadin and Slenyto.

Names and forms

The pharmacology literature gives the chemical name as 5-methoxy-N-acetyltryptamine. In everyday use the word melatonin covers three different things: the hormone the body makes (endogenous melatonin), manufactured melatonin products sold as supplements, and licensed melatonin medicines. NCCIH states that supplements are most often made synthetically.

Supplement versus prescription medicine

How a melatonin product is classed depends on the country. NCCIH and the CDC describe it in the United States as a dietary supplement, a category with less strict oversight than prescription drugs. The NHS describes melatonin as a medicine used for sleep problems: it states that most adults aged 55 or older can take it for short-term sleep problems, that adults under 55 may take it on specialist advice, and that children can take it for longer-term sleep problems only if a specialist recommends it.

Role in the sleep-wake cycle

Tordjman and colleagues report that melatonin regulates sleep-wake rhythms, neuroendocrine rhythms and body temperature cycles through MT1 and MT2 receptors. After oral administration, plasma levels peak within about an hour and then decline quickly, which the review describes with half-lives of roughly 2 and 20 minutes. NCCIH summarizes the same physiology in plain terms: the brain produces melatonin in response to darkness, and the hormone helps regulate circadian rhythms and sleep.

What supplementation involves

Supplementation means taking manufactured melatonin by mouth, in forms such as tablets and gummies, in addition to the body's own production. Products differ between manufacturers and formats, and a 2023 JAMA analysis of gummies found that measured melatonin content often differed from the label (see Safety and Suitability). This page gives no doses, timing or product advice.

Related Machipedia pages include Dietary Supplements, which describes the wider supplement category, as well as Magnesium Supplementation, Dinacharya, Hypnotherapy, Binaural Beats and Mindfulness. Each of those pages has its own summary, and the sources reviewed for this page do not compare those practices with melatonin.

Sleep and circadian uses

NCCIH describes melatonin supplements as used for sleep problems such as insomnia, for jet lag, and for sleep difficulties in children. The NHS lists licensed melatonin for short-term sleep problems in older adults and, under specialist care, for longer-term sleep problems in children. The American Academy of Sleep Medicine has also issued a guideline on circadian rhythm sleep-wake disorders that addresses strategically timed melatonin for specific conditions.

Other uses studied

Researchers have also examined melatonin for sleep problems in shift workers, sleep in children with neurological and psychiatric conditions, delirium prevention in hospitalized patients, and anxiety before surgery. An umbrella review of 195 reviews found that melatonin had been studied across a wide range of health outcomes, and that most of those reviews were of low methodological quality.

Insomnia in adults

A 2005 meta-analysis by Brzezinski and colleagues pooled 17 studies with 284 participants and reported that melatonin shortened sleep onset latency by about 4.0 minutes (95% CI 2.5 to 5.4) and lengthened total sleep by about 12.8 minutes (95% CI 2.9 to 22.8) compared with placebo. A 2013 meta-analysis by Ferracioli-Oda and colleagues of 19 placebo-controlled trials with 1,683 adults and children with primary sleep disorders reported about 7.06 minutes shorter sleep latency and 8.25 minutes more total sleep time, effects the authors called modest.

A 2022 network meta-analysis in The Lancet of 154 randomized trials found several benzodiazepines and related drugs more efficacious than melatonin in acute treatment and concluded that melatonin did not show overall material benefits. The 2017 American Academy of Sleep Medicine guideline on chronic insomnia in adults made a weak recommendation that clinicians not use melatonin for sleep onset or maintenance insomnia, which it describes as lower certainty rather than a finding of ineffectiveness. NCCIH states that evidence is insufficient to recommend melatonin for chronic insomnia.

Circadian disorders, jet lag and shift work

The 2015 American Academy of Sleep Medicine guideline on circadian rhythm sleep-wake disorders endorsed, at a second-tier degree of confidence, strategically timed melatonin for delayed sleep-wake phase disorder, for blind adults with non-24-hour sleep-wake rhythm disorder, and for children and adolescents with irregular sleep-wake rhythm disorder and comorbid neurological disorders, and recommended against it for older adults with dementia. This guideline is separate from the 2017 insomnia guideline.

A Cochrane review by Herxheimer and Petrie, published in 2002, included ten trials and reported that nine found melatonin reduced jet lag after flights crossing five or more time zones. A 2022 systematic review of 10 trials in health care shift workers reported less daytime sleepiness and shorter sleep onset latency, but graded the evidence 1- under SIGN criteria and noted wide variation, small samples and young participants. NCCIH states that jet lag evidence comes largely from small, older reviews.

Children, delirium and surgery

A 2025 meta-analysis of 21 studies in children with neurological and psychiatric conditions reported that melatonin significantly reduced sleep onset latency and increased sleep efficiency and total sleep time compared with placebo. NCCIH states that benefits in children appeared in small, brief studies and that long-term effects are uncertain.

A 2026 network meta-analysis of 33 trials with 5,045 hospitalized patients associated melatonin and melatonin receptor agonists with a lower delirium risk than non-active controls (relative risk 0.77, 95% CI 0.64 to 0.92), with low to moderate certainty. In a network meta-analysis of 48 trials of premedication in children aged 1 to 7, melatonin did not differ from placebo for sedation at induction or mask acceptance but was superior for reducing emergence delirium.

Reported adverse effects and cautions

A 2016 safety review by Andersen and colleagues reported that short-term use was associated with mild adverse effects such as dizziness, headache, nausea and sleepiness, and that no studies indicated serious adverse effects. It stated that long-term safety in children and adolescents requires further investigation and that, because of a lack of human studies, pregnant and breastfeeding women should not take melatonin. NCCIH likewise states that the long-term effects are unclear and that research on pregnancy and breastfeeding is lacking.

The NHS states that melatonin is not usually recommended during pregnancy because little is known about its effect on babies. It states that breastfeeding may be possible if a doctor or health visitor says the baby is healthy, but that longer use might make the baby sleepy. The NHS advises people with a past allergic reaction to melatonin, liver or kidney problems, or autoimmune conditions such as rheumatoid arthritis, multiple sclerosis or lupus to speak to a doctor or pharmacist first. NCCIH and the Cochrane jet lag review both report that people with epilepsy and people taking blood thinners such as warfarin need medical supervision, the latter based on case reports.

Children and accidental ingestion

A 2022 CDC report analyzed National Poison Data System records and counted 260,435 pediatric melatonin ingestions between 2012 and 2021, with the annual number increasing 530%. Pediatric melatonin ingestions made up 4.9% of all pediatric ingestions reported in 2021 compared with 0.6% in 2012. Hospitalizations and more serious outcomes increased, mainly from unintentional ingestions by children aged 5 and younger. Five children required mechanical ventilation and two died. The authors called for public awareness and preventive measures, and noted that poison center data are voluntary and may undercount exposures.

Product quality and labeling

A 2023 JAMA research letter by Cohen and colleagues tested 25 melatonin gummy products sold in the United States. Twenty-two were inaccurately labeled, and measured melatonin ranged from 74% to 347% of the labeled amount. One product contained no detectable melatonin but contained cannabidiol (CBD). The authors estimated that taking gummies as directed could expose children to many times the melatonin level that produces normal nighttime blood levels in young adults. Limitations included a small sample, one sample per brand and gummies only, so the findings do not describe other product forms.

Who should ask a clinician

Sources reviewed advise speaking with a health care professional before use by children, people who are pregnant or breastfeeding, people with epilepsy, liver or kidney disease or autoimmune conditions, and people taking blood thinners or other medicines. NCCIH names cognitive behavioral therapy for insomnia as the recommended first treatment for chronic insomnia. Persistent sleep problems warrant professional assessment, and this page does not replace medical care.