Melatonin
Melatonin is a hormone your body makes to help control sleep. A Cochrane review found it prevents or reduces jet lag on long flights, and it modestly shortens the time it takes to fall asleep. In a 2024 analysis, the effect grew with dose up to about 4 mg.
Melatonin is a hormone made by the pineal gland that helps control the sleep-wake cycle. Its exact mechanism isn't known, but it's thought to control the body's circadian pacemaker and promote sleep.
Research & evidence
Strong support Some support Weak or no supportColours show how well the sources back each point. The reason is next to each one.
A Cochrane review found melatonin "remarkably effective" for preventing jet lag on flights crossing five or more time zones. Its widely-cited number-needed-to-treat of 2 comes with an important caveat, disclosed by the reviewers themselves: it was calculated from only two of the ten included trials (46 travellers total), since the rest didn't report the type of data needed for that calculation.
Moderate evidenceSome support. Shown only in certain groups, uses, strains or doses
Study details
Herxheimer & Petrie 2002 (Cochrane): 10 trials met inclusion criteria; per the currently-live review text, "eight of the ten trials found that melatonin... decreased jet lag". The NNT of 2 is explicitly caveated by Cochrane itself as resting on just 2 of the 10 trials (46 travellers). Doses of 0.5-5mg tested; above 5mg "appear to be no more effective." Disclosed conflict: co-author Keith Petrie "undertaken two of the trials reviewed" — one of two reviewers assessing trial quality also ran two of the ten trials assessed, openly disclosed by Cochrane. Funding: internal/academic only (University of Auckland, UK Cochrane Centre), no industry money.
Source: Herxheimer A, Petrie KJ. "Melatonin for the prevention and treatment of jet lag." Cochrane Database Syst Rev. 2002 Apr 22;2002(2):CD001520; critique: "Can Melatonin Prevent or Treat Jet Lag?" American Family Physician, Dec 1, 2002. View source
Melatonin modestly reduces the time it takes to fall asleep (sleep onset latency), though the effect size is smaller than many people expect from a 'sleep supplement.'
Strong evidenceStrong support. Several trials or reviews agree
Study details
Cruz-Sanabria et al. 2024 (26 RCTs, 1,689 observations, 1987-2020): "melatonin gradually reduces sleep onset latency and increases total sleep time." Ferracioli-Oda et al. 2013 (19 studies, 1,683 subjects, pooling insomnia/delayed sleep phase/REM sleep behavior disorder): weighted mean reduction in sleep latency of 7.06 minutes (95% CI 4.37-9.75, p<0.001). Neither source shows meaningful industry funding: Cruz-Sanabria's senior author cofounded a sleep-diagnostics/wearable company (unrelated to melatonin sales), funded by academic/public sources (Arpa Foundation, Italian Ministry of Health); Ferracioli-Oda's senior author disclosed unrelated early-career fellowships, with funders having "no role in study design, data collection and analysis, decision to publish." Cruz-Sanabria caveats its own findings as "based on predicted data" requiring clinical replication, and notes possible publication bias via funnel-plot asymmetry.
Source: Cruz-Sanabria F, Bruno S, Crippa A, et al. "Optimizing the Time and Dose of Melatonin as a Sleep-Promoting Drug." J Pineal Res. 2024 Aug;76(5):e12985; Ferracioli-Oda E, Qawasmi A, Bloch MH. "Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders." PLoS ONE. 2013 May 17;8(5):e63773. View source
A 2024 dose-response meta-analysis (26 RCTs, 1,689 observations) found melatonin's sleep-promoting effect increases progressively with dose, peaking at 4 mg/day — higher doses within that range outperformed lower ones for sleep-onset latency and total sleep time, rather than lower and higher doses being similarly effective.
Moderate evidenceSome support. Based mainly on one review or trial
Study details
Cruz-Sanabria et al. 2024: "advancing the time of administration to 3 h before bedtime, using doses ranging between 2 and 4 mg, will enhance exo-MEL's sleep-promoting action" — an increasing dose-response relationship, not a flat one. Ferracioli-Oda et al. 2013 also found: "trials... using higher doses of melatonin demonstrated greater effects on decreasing sleep latency and increasing total sleep time." One nuance: Ferracioli-Oda found "no significant effects of trial duration and melatonin dose... on sleep quality" specifically (as distinct from sleep-onset latency/total sleep time) — so the dose-response relationship may not extend to subjective sleep-quality ratings. Cruz-Sanabria's dose-response curve is explicitly described as "based on predicted data" requiring clinical replication, and the tested dose range excluded anything above 10mg/day, so the curve's peak at 4mg doesn't establish that doses above the tested range would continue improving.
Source: Cruz-Sanabria F, Bruno S, Crippa A, et al. "Optimizing the Time and Dose of Melatonin as a Sleep-Promoting Drug." J Pineal Res. 2024 Aug;76(5):e12985; Ferracioli-Oda E, Qawasmi A, Bloch MH. "Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders." PLoS ONE. 2013 May 17;8(5):e63773. View source
Dosage
| Form | Amount |
|---|---|
| Any form | No standard dose is listed by our sources. In a 2024 analysis of 26 trials, the sleep-promoting effect grew with dose up to about 4 mg a day and was greater when melatonin was taken about 3 hours before bedtime. Cochrane's jet-lag review says doses above 5 mg appear to be no more effective. |
Side effects
Side effects in short-term studies were mild: sleepiness, headache, dizziness and nausea. Don't drive until you know how it affects you, and keep it away from children.
Well documented Reported (case reports, anecdotal or one study) None reportedThe circle shows how well documented an effect is, not how serious it is. A rarely reported effect can still be serious, so always read ‘When to stop’.
| Effect | Frequency | When to stop |
|---|---|---|
| Sleepiness, or daytime drowsiness (especially in older adults)Well documentedListed plainly by NIH, MSK or LiverTox | Mild; reported in short-term studies | Don't drive until you know how it affects you; lower the dose or stop if it carries into the next day. |
| Headache, dizziness or nauseaWell documentedListed plainly by NIH, MSK or LiverTox | Mild; reported in short-term studies | Stop and talk to a doctor if it persists. |
| Bad dreamsWell documentedListed plainly by NIH, MSK or LiverTox | Not stated | Lower the dose or stop if they bother you. |
| Confusion, fast heartbeat, flushing, itching, stomach cramps or low body temperatureWell documentedListed plainly by NIH, MSK or LiverTox | Not stated | Stop and see a doctor if these happen. |
| Worsening of myasthenia gravisReportedCase reports only | 3 reported cases; MSK says likely due to immune effects and an interaction with corticosteroids or other immunosuppressants | If you have myasthenia gravis, talk to your doctor before taking melatonin, and see a doctor if it gets worse. |
Safety & interactions
Safety
Short-term use appears to be safe for most people, and only mild side effects, such as headache, dizziness, nausea and sleepiness, were reported in short-term studies. Information on long-term safety is lacking. Melatonin can cause drowsiness, so don't drive or operate heavy machinery until you know how it affects you. Labels may not match what's in the bottle: in a 2023 study, 22 of 25 melatonin gummy products were inaccurately labeled; one had no detectable melatonin, and the rest had 74% to 347% of the listed amount.
Contraindications
Talk to your doctor first if you have a hormone-sensitive cancer, such as breast or prostate cancer: melatonin can change the amount of estrogen in your body, which may worsen your condition. People with epilepsy and people taking blood thinners should take melatonin only under medical supervision. The American Academy of Sleep Medicine's 2015 guidelines recommend against melatonin for people with dementia. There's been little research on its safety during pregnancy or breastfeeding. Talk to a pediatrician before giving melatonin to a child, and keep it in a safe place out of children's reach: too much melatonin can cause serious side effects in children under 3, including trouble breathing and death.
Drug interactions
Oral melatonin is associated with lower levels of factor VIII and fibrinogen (blood-clotting proteins), which may increase the risk of side effects with blood thinners, and MSK advises checking with your provider if you take warfarin. NCCIH says people taking blood thinners should take melatonin only under medical supervision.
MSK says taking melatonin with nifedipine (a blood pressure medicine) can raise blood pressure and heart rate.
MSK says melatonin inhibits CYP1A2, an enzyme the body uses to break down some drugs, and may raise levels of drugs it processes, such as fluvoxamine. The two studies MSK cites on fluvoxamine found the reverse: fluvoxamine (an antidepressant) raised melatonin levels when the two were taken together.
Established: stated plainly by an authoritative source. Documented: supported by case reports or trial data. Theoretical: based on mechanism, animal data, or a cautious listing. Always check with your pharmacist or prescriber.
Combining with other herbs
Avoid combining with
Which form to buy
Gummies
Weaker choiceMost products tested were mislabeled
In a 2023 test, 22 of 25 melatonin gummy products were mislabeled: one had no detectable melatonin, and the rest had 74% to 347% of the labeled amount.
Melatonin supplements in general
Works, with a catchTesting found label amounts often inaccurate
In a 2017 test of 31 melatonin supplements bought from grocery stores and pharmacies, most didn't contain the amount on the label, and 26% contained serotonin, a hormone that can be harmful even at low levels.