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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Melatonin

The Hormone of Darkness

Evidence grade 4 of 5, Strong. Read how the Atlas grades evidence.

40 human trials, about 400 studies, >15,000 participants. The written rationale for this grade is still being prepared.

FDA
OTC supplement (US); Rx in EU
WADA
Not prohibited

Reference only. Not medical advice.

What can go wrong

Short-term, low-dose melatonin is generally well tolerated, but several real cautions apply. Supraphysiologic doses (the common US 5-10 mg) are not more effective for circadian shifting and may cause next-day grogginess; taken at the wrong time of day, melatonin can shift the clock the wrong way. US products are regulated as supplements, and independent testing has documented wide dose inaccuracy and undeclared serotonin and CBD, so the dose on the label may not be the dose in the bottle. A preliminary 2025 American Heart Association conference abstract (not peer-reviewed, observational, cannot show cause and effect) associated long-term melatonin use with higher heart-failure risk in people with insomnia and warrants caution about chronic high-dose use pending peer review. Pediatric use, pregnancy, and use alongside sedatives, blood thinners, or for diagnosed mood or sleep disorders should be directed by a qualified healthcare provider; this entry gives no dosing or protocol for those situations.

Melatonin is best understood in two registers that the marketing blurs together. Endogenously it is the darkness hormone: the pineal gland releases it in dim and dark conditions to tell the body it is night, light suppresses it, and its evening rise is the gold-standard marker of a person's circadian phase. As a supplement it is a timing signal, not a sedative; the strongest support is for low-dose, correctly-timed use in jet lag, delayed sleep-wake phase disorder, and shift-work circadian shifting. Evidence that it meaningfully improves ordinary sleep in healthy adults is weak, with pooled effects of roughly seven minutes of sleep latency. Most US products contain 5 to 10 mg, about ten times the physiologically relevant dose, and independent testing has found wide content inaccuracy and undeclared serotonin and CBD.

Not a sleeping pill, a darkness signal. And most people take 10x too much.

What people take it for

What it is taken for. Approval, where it exists, covers only some of these.

  • Jet lag across 5 or more time zones (strongest supplement evidence; Cochrane review)
  • Delayed sleep-wake phase disorder (AASM-endorsed, strategically timed, low dose)
  • Shift-work circadian re-entrainment (phase-shifting, not sedation)
  • Sleep-onset support in primary sleep disorders (modest effect, about 7 minutes)
  • Circadian phase measurement via dim-light melatonin onset (DLMO) as a research and clinical marker

What people get wrong

  • Often saidMelatonin is a sleeping pill, and more is better

    ActuallyIt is a timing signal, not a sedative. Low-dose (0.5-1 mg) shifts the circadian clock about as well as much higher doses; in a simulated night-shift RCT, 0.5 mg phase-advanced the clock comparably to 3 mg (Sharkey & Eastman 2001). The AASM 2017 guideline issues a weak recommendation against using melatonin for ordinary adult insomnia, and the pooled benefit on sleep latency is only about 7 minutes (Ferracioli-Oda 2013).

  • Often saidMelatonin gummies are safe for kids to use freely and long-term

    ActuallyThere is no long-term pediatric safety data. US pediatric ingestions reported to poison control rose 530% from 2012 to 2021 (CDC MMWR, Lelak 2022), and 88% of tested gummies were inaccurately labeled, with measured melatonin ranging 74-347% of the stated amount and some containing undeclared CBD (Cohen, JAMA 2023). European regulators keep pediatric melatonin medicines (such as Slenyto) prescription-only. Pediatric use is a question for a qualified clinician, not a self-serve decision.

  • Often saidA melatonin supplement reliably contains the dose printed on the label

    ActuallyIndependent testing found content ranging from -83% to +478% of the label across 31 products, with 71% off by more than 10% and serotonin (a strictly controlled compound) present in 8 of 31 (Erland & Saxena, JCSM 2017). US melatonin is regulated as a dietary supplement, not a drug, so there is no federal pre-market requirement to verify content.

  • Often saidMelatonin and endogenous melatonin are the same kind of evidence

    ActuallyThey are not. That the pineal gland secretes melatonin in darkness and that its evening rise marks circadian phase (DLMO) is settled physiology. Whether a 5 mg gummy improves your sleep tonight is a separate, weaker question. The strong science is about the signal; the marketing borrows that strength for the pill.

Who profits, and who pushes back

  • Sleep-medicine community

    Promotes itClinical

    Endorses low-dose, correctly-timed melatonin for jet lag and circadian shifting; cautious about routine sleep use.

  • US supplement industry

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    Promotes itCommercial

    Sells high-dose melatonin (often 5-10mg) and pediatric gummies; commercial interest in the "more is better" framing.

  • American Academy of Sleep Medicine

    Pushes backSleep-medicine clinical guideline body

    The 2017 chronic-insomnia guideline suggests that clinicians not use melatonin as a treatment for sleep-onset or sleep-maintenance insomnia in adults, citing small benefit observed only in very low-quality trials.

  • Pieter A. Cohen and colleagues

    Pushes backHarvard / Cambridge Health Alliance; JAMA 2023 gummy analysis

    The authors reported that 22 of 25 melatonin gummy products were inaccurately labeled and warned that pediatric use of melatonin gummies may result in ingestion of unpredictable quantities of melatonin and CBD.

  • Lauren Erland and Praveen Saxena

    Pushes backUniversity of Guelph; JCSM 2017 content analysis

    The investigators found melatonin content ranging from -83% to +478% of the labeled amount and identified serotonin, a strictly controlled compound, in eight of the products tested.

  • Marie-Pierre St-Onge

    Pushes backColumbia University; chair, AHA 2025 sleep-health scientific statement

    St-Onge has noted that melatonin is not indicated for the treatment of insomnia in the US, in the context of the AHA's preliminary findings on long-term melatonin use and heart-failure risk.

Where the research comes from

Share of published research by country of origin.
PlaceShare of published research
USA46%
Europe28%
Other26%

Research published from: Global.

How we got here

The pineal gland was treated as a seat of consciousness in classical and South Asian thought (Descartes later called it the seat of the soul, while yogic traditions linked the region to the ajna chakra), but melatonin itself was a 20th-century isolation. In 1917 American researchers McCord and Allen showed bovine pineal extract lightened the skin of tadpoles. Working from that neglected paper, Yale dermatologist Aaron Lerner and colleagues isolated and named melatonin in 1958 from bovine pineal glands, after a roughly four-year effort, naming it for its skin-lightening action on amphibians. Through the 1960s and 1970s Julius Axelrod and Richard Wurtman mapped its rhythmic, light-controlled secretion, establishing it as the body's darkness and timing signal rather than a sleep inducer. By the 1990s it was sold over the counter in the United States while much of Europe kept melatonin medicines prescription-only, and pediatric use later surged without long-term safety data.

  1. 1917McCord and Allen show bovine pineal extract lightens amphibian skin
  2. 1958Aaron Lerner and colleagues at Yale isolate and name melatonin from bovine pineal glands
  3. 1960s-1970sAxelrod and Wurtman map light-controlled, rhythmic pineal secretion; darkness/timing role established
  4. 1989Lewy and colleagues define dim-light melatonin onset (DLMO) as a circadian phase marker
  5. 1990sSold over the counter in the US; much of Europe keeps melatonin medicines prescription-only
  6. 2002Cochrane jet-lag review (Herxheimer & Petrie) finds melatonin reduces jet lag across 5+ time zones
  7. 2007-2018EMA authorizes prescription prolonged-release melatonin: Circadin (adults 55+, 2007) and Slenyto (children with ASD, 2018)
  8. 2013Ferracioli-Oda meta-analysis: modest pooled sleep effects (about 7 minutes faster onset)
  9. 2017Erland and Saxena (JCSM) find wide content inaccuracy and undeclared serotonin in US/Canada supplements
  10. 2017AASM chronic-insomnia guideline issues a weak recommendation against melatonin for adult insomnia
  11. 2022CDC MMWR reports US pediatric melatonin ingestions rose 530% over 2012-2021
  12. 2023Cohen (JAMA) finds 88% of US melatonin gummies inaccurately labeled, some with undeclared CBD

At a glance

What it is
Darkness/timing signal
Effective dose
0.5-1 mg
Typical US dose
5-10 mg (too high)
Best for
Jet lag, delayed sleep phase

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Melatonin. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources