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Research · Supplements

Melatonin

In people with primary sleep disorders, melatonin shortened time to fall asleep by about 7 minutes and lengthened sleep by about 8 minutes. Nine of ten jet lag trials found less jet lag after flights across five or more time zones. Products often contain a different dose than labeled. Pediatric ingestions rose 530% in a decade.

Add to Bio HackChecked 2026-11-09
Status
Dietary supplement in the US. Licensed as a medicine in the UK, including for short-term jet lag.
Also called
N-acetyl-5-methoxytryptamine, melatonin gummies, sleep gummies, prolonged-release melatonin, Circadin
Taken for
falling asleep, sleep quality, insomnia, jet lag, shift work, sleep in children

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help5

Reported risks7

What people take it for, and what was found

Shown to help5

Moderate

Time to fall asleep and total sleep in sleep disorders

Shown to shorten time to fall asleep about 7 minutes and add about 8 minutes of sleep in people with primary sleep disorders.

The numbers and sources
Effect
Across 19 studies (1,683 subjects) with primary sleep disorders, melatonin reduced sleep onset latency by 7.06 minutes (95% CI 4.37 to 9.75), increased total sleep time by 8.25 minutes (95% CI 1.74 to 14.75), and improved sleep quality (SMD 0.22, 95% CI 0.12 to 0.32). Longer trials and higher doses showed larger effects on latency and total sleep, and the effects did not fade with continued use [1].
Population
Adults and children with primary sleep disorders [1].
Sources
[1]
Caveats
The authors note the absolute benefit is smaller than with other insomnia drugs [1].
Moderate

Sleep quality in adults with other conditions

Shown to improve sleep quality scores about 1.2 points in adults with other conditions, with results varying by condition and no clear change in cancer.

The numbers and sources
Effect
Across 23 RCTs, Pittsburgh Sleep Quality Index scores improved by 1.24 points (95% CI -1.77 to -0.71, I² 80.7%). Improvements were 2.20 points in respiratory diseases, 2.74 in metabolic disorders and 0.67 in sleep disorders, with no effect found in mental disorders or neurodegenerative diseases [2]. Later reviews in neurodegenerative disease differ. In Parkinson's disease, PSQI scores improved by 1.75 points across 7 RCTs (409 patients, 95% CI -2.94 to -0.55) [3], and by 2.90 points at doses above 4 mg but not at 4 mg or less across 5 RCTs (206 patients) [4]. In 10 RCTs of adults 65 and over with mild cognitive impairment or dementia (516 people), total sleep time rose by 12.4 minutes (95% CI 8.1 to 16.7) [5]. In 7 pooled trials in people with cancer, sleep quality did not change significantly (SMD -0.85, 95% CI -2.46 to 0.76, I² 94.5%) [6].
Population
Adults with respiratory, metabolic, sleep and other disorders [2]; people with Parkinson's disease [3][4]; older adults with cognitive impairment [5]; people with cancer [6].
Sources
[2], [3], [4], [5], [6]
Caveats
Heterogeneity was high, and health status explained part of it [2]. The Parkinson's improvements in subjective sleep quality did not reach the minimal clinically important difference [3]. Heterogeneity was 72% for total sleep time in [5] and 94.5% in [6].
Moderate

Jet lag

Shown to reduce jet lag after flights crossing five or more time zones when taken near bedtime at the destination. Doses above 5 mg did no better.

The numbers and sources
Effect
Nine of ten trials found melatonin taken near target bedtime at the destination (10 pm to midnight) reduced jet lag after flights crossing five or more time zones. Doses of 0.5 to 5 mg gave similar results, people fell asleep faster after 5 mg than 0.5 mg, and doses above 5 mg did no better. The number needed to treat was 2. Benefit was smaller for westward flights, and dosing early in the day was liable to cause sleepiness and delay adaptation [7].
Population
Airline passengers, airline staff and military personnel in 10 RCTs [7].
Sources
[7]
Caveats
The review dates from 2002. One of the ten trials had a design fault and could not be used [7].
ModerateStudied in children

Sleep in children

Shown to improve sleep onset or sleep time in children with autism, cerebral palsy, atopic dermatitis or other neurologic conditions. No data in typically developing young children.

The numbers and sources
Effect
In children with autism, melatonin improved sleep quality (Hedges' g 0.75) and total sleep time (g 0.58) [8]. In 3 RCTs in children with atopic dermatitis, 3 to 6 mg a day shortened sleep onset latency (SMD -0.63, 95% CI -1.00 to -0.26) without a significant change in total sleep time (18.29 minutes, 95% CI -10.31 to 46.88) [9]. In 120 children aged 3 to 12 with cerebral palsy, 3 to 10 mg a day for 12 weeks gave 1.31 hours more total sleep and 27.72 minutes faster sleep onset than placebo [10]. A systematic review of children aged 0 to 6 found 6 trials (167 children), all in children with neurologic conditions, that reported improved sleep onset with few adverse events [11].
Population
Children with autism [8], atopic dermatitis [9], cerebral palsy [10] or other neurologic conditions [11].
Sources
[8], [9], [10], [11]
Caveats
No efficacy data were found for young children with typical development, and long-term outcomes were absent [11]. The atopic dermatitis review pooled only 3 trials [9].
LimitedStudied in women

Shift work

One trial found better sleep quality on days off in nurses on shift work who took 0.3 mg on nights off, with no change in sleep duration.

The numbers and sources
Effect
In 46 nurses on fixed shifts, 0.3 mg of melatonin taken on nights off improved self-reported sleep quality on days off by 35.33% (p < 0.001) and lowered climacteric symptoms by 15.8% against placebo (p = 0.01). Total sleep duration did not change [12].
Population
Climacteric women working morning, afternoon or night shifts in one hospital [12].
Sources
[12]
Caveats
One small trial, retrospectively registered. Melatonin was taken on nights off, so the trial does not show effects on sleep after night shifts.

Doses studied

Sleep trials used 0.15 to 12 mg a day, mostly for 4 weeks or less, up to 29 weeks [13]. Jet lag trials used 0.5 to 5 mg near local bedtime, and 2 mg slow-release showed relatively little effect [7]. Measured product content often differs from the label [14][15].

Risks

Reported risks7

ModerateCommon

Side effects in trials

Daytime sleepiness was the most frequent side effect in trials, at about 1.7%, followed by headache and dizziness, with few serious events.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
Across 37 RCTs, the most frequent adverse events were daytime sleepiness (1.66%), headache (0.74%), other sleep-related events (0.74%), dizziness (0.74%) and hypothermia (0.62%). Few serious events were reported. Agitation, fatigue, mood swings, nightmares, skin irritation and palpitations were listed as of possible clinical significance [13].
Population
RCTs of melatonin for primary or secondary sleep disorders [13].
Sources
[13]
Caveats
Most trials ran 4 weeks or less, and only 8 of 37 met the top risk-of-bias rating. Long-term data are scarce [13].
ModerateHow often is not known

Product content does not match the label

Product tests found melatonin far from the label, up to 478% in supplements and 347% in gummies. Some contained serotonin or CBD.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In 31 commercial supplements, melatonin ranged from -83% to +478% of labeled content, and lot-to-lot variation in one product reached 465%. More than 71% were outside 10% of label, and 8 contained serotonin at 1 to 75 µg [14]. In 25 US melatonin gummy products, measured melatonin ranged from 74% to 347% of label, and 22 of 25 were inaccurately labeled. One product contained no detectable melatonin and 31.3 mg of CBD [15].
Population
Product testing [14][15][16].
Sources
[14], [15], [16]
Caveats
Two snapshots of two markets. No serotonin was found in the US gummies [15]. In a 2025 survey of 110 US supplements marketed for children, analyzed by FDA scientists, melatonin was found in 108 and ranged from 0% to 667% of the label, with servings of 0.042 to 50 mg [16].
ModerateStudied in childrenHow often is not known

Ingestions by children

Linked to a 530% rise in reported child ingestions in the US from 2012 to 2021, mostly in children 5 and under, with two deaths.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
From 2012 to 2021, 260,435 pediatric melatonin ingestions were reported to US poison centers, and annual ingestions rose 530%. Melatonin went from 0.6% to 4.9% of all pediatric ingestions reported. Hospitalizations and serious outcomes rose, mostly unintentional ingestions in children 5 and under. Five children required mechanical ventilation and two died [17]. A 2026 systematic review of 12 observational studies from US, Nordic, Australian and Portuguese registries and poison data documented rising prescribing, extended use and overdoses in children aged 0 to 6, especially in the past decade [11].
Population
US National Poison Data System, ages 19 and under [17]; registry and poisoning studies in young children [11].
Sources
[17], [11]
Caveats
Poison center reports, not a measure of toxicity per dose.
LimitedHow often is not known

Epilepsy and warfarin

Case reports: people with epilepsy and people taking warfarin may have come to harm from melatonin.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Case reports reviewed in the Cochrane jet lag review suggest people with epilepsy and patients taking warfarin may come to harm from melatonin [7].
Population
Case reports [7].
Sources
[7]
Caveats
The review called for investigation of both and gave no rates [7].
LimitedHow often is not known

Glucose tolerance in carriers of a diabetes risk gene

One trial found a single 5 mg dose worsened glucose tolerance about 12% in carriers of the MTNR1B diabetes risk variant, not in noncarriers.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In a crossover trial, a single 5 mg dose worsened glucose tolerance by 11.7% (95% CI 1.0 to 22.3) and cut early C-peptide response by 19.2% against placebo in carriers of the MTNR1B risk variant. Noncarriers showed no such change [18].
Population
21 healthy adults of European ancestry, 10 of them risk-variant carriers [18].
Sources
[18]
Caveats
Laboratory glucose tests on single dosing days. Long-term diabetes risk was not measured.
LimitedHow often is not known

Liver enzyme rises at 300 mg a day

One small trial at 300 mg a day was stopped when 3 of 4 patients had liver enzyme rises, which resolved after stopping.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
A trial of 300 mg a day as add-on therapy in primary progressive multiple sclerosis was stopped after 3 of 4 patients on melatonin developed grade 1 to 2 liver enzyme rises, which resolved after stopping. All 3 took other drugs that share liver metabolism with melatonin [19].
Population
8 patients randomized before the trial was halted [19].
Sources
[19]
Caveats
Very small numbers. The dose is far above sleep doses. A drug interaction is the authors' post hoc explanation.
LimitedHow often is not known

Heart rhythm events

Case reports: heart rhythm disturbances on melatonin improved after people stopped it.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
A 63-year-old man taking 10 mg a day developed a heart rhythm disturbance that resolved after he stopped melatonin. A systematic review of published reports found similar arrhythmic events that improved after discontinuation [20].
Population
Case reports [20].
Sources
[20]
Caveats
Case reports cannot show cause or give rates.

Claims tested and not found

  1. That more melatonin gives more jet lag relief. Doses above 5 mg did no better than 5 mg [7].
  2. That melatonin improves sleep quality in mental disorders. The subgroup with mental disorders did not show an effect on PSQI scores [2].

Sources

  1. Ferracioli-Oda E, Qawasmi A, Bloch MH. Meta-analysis: melatonin for the treatment of primary sleep disorders. PLoS ONE. 2013. https://doi.org/10.1371/journal.pone.0063773
  2. Fatemeh G, Sajjad M, Niloufar R, et al. Effect of melatonin supplementation on sleep quality: a systematic review and meta-analysis of randomized controlled trials. Journal of Neurology. 2022. https://doi.org/10.1007/s00415-020-10381-w
  3. Yousef O, Abouelmagd ME, Khaddam H, et al. The Effectiveness of Melatonin for Sleep Disturbances in Parkinson' Disease: Systematic Review and Meta-Analysis. Journal of Sleep Research. 2026. https://doi.org/10.1111/jsr.70097
  4. Zrineh A, Akwan R, Elsharkawy MM, et al. The effect of melatonin on sleep quality and daytime sleepiness in Parkinson's disease: A systematic review and meta-analysis of randomized placebo-controlled trials. Sleep Medicine. 2025. https://doi.org/10.1016/j.sleep.2025.106540
  5. Mdluli NT, Banda KJ, Chang YC. Melatonin for sleep and cognitive outcomes in older adults with cognitive impairment: a meta-analysis of randomised controlled trials. Age and Ageing. 2025. https://doi.org/10.1093/ageing/afaf333
  6. Abbasi MM, Pasha S, Khosravi F, et al. Safety and Efficacy of Melatonin for Sleep Disorders in Cancer: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Current Reviews in Clinical and Experimental Pharmacology. 2026. https://doi.org/10.2174/0127724328470308260825053321
  7. Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews. 2002. https://doi.org/10.1002/14651858.CD001520
  8. Yang H, Lu F, Zhao X. Factors influencing the effect of melatonin on sleep quality in children with autism spectrum disorder: a systematic review and meta-analysis. Sleep and Breathing. 2025. https://doi.org/10.1007/s11325-025-03432-x
  9. Alghamdi F, Alzahrani DY, Alharthy RF, et al. Effectiveness of melatonin supplementation for improving sleep quality and disease severity in children with atopic dermatitis: a systematic review and meta-analysis. Frontiers in Medicine. 2026. https://doi.org/10.3389/fmed.2025.1718859
  10. K GP, Mundada S, Zambani J, et al. Oral Melatonin Supplementation for Sleep Disturbances in Children with Cerebral Palsy: A Randomized Double-Blind Controlled Trial. Indian Journal of Pediatrics. 2026. https://doi.org/10.1007/s12098-025-05873-4
  11. Kracht CL, Bolamperti G, Breeden R, et al. Melatonin Use in Young Children: A Systematic Review. JAMA Network Open. 2026. https://doi.org/10.1001/jamanetworkopen.2025.51958
  12. Saraiva SP, D'Aurea CVR, Luz CSS, et al. Low-Dose Melatonin, Climacteric Symptoms and Sleep in Female Shift Workers: A Randomized Controlled Trial. Journal of Pineal Research. 2026. https://doi.org/10.1111/jpi.70140
  13. Besag FMC, Vasey MJ, Lao KSJ, et al. Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review. CNS Drugs. 2019. https://doi.org/10.1007/s40263-019-00680-w
  14. Erland LA, Saxena PK. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content. Journal of Clinical Sleep Medicine. 2017. https://doi.org/10.5664/jcsm.6462
  15. Cohen PA, Avula B, Wang YH, et al. Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. JAMA. 2023. https://doi.org/10.1001/jama.2023.2296
  16. Pawar RS, Coppin JP, Khanna S, Parker CH. A Survey of Melatonin in Dietary Supplement Products Sold in the United States. Drug Testing and Analysis. 2025. https://doi.org/10.1002/dta.3823
  17. Lelak K, Vohra V, Neuman MI, et al. Pediatric Melatonin Ingestions: United States, 2012 to 2021. MMWR Morbidity and Mortality Weekly Report. 2022. https://doi.org/10.15585/mmwr.mm7122a1
  18. Qian J, Stefanovski D, Andersen PAK, et al. Melatonin Impairs Glucose Tolerance, First-Phase Insulin Secretion, and Insulin Feedback Inhibition; Interaction With MTNR1B Diabetes Risk Variant. Diabetes Care. 2026. https://doi.org/10.2337/dc26-0164
  19. Bejarano I, Jiménez-Jorge S, Lobo-Acosta MÁ, et al. Hepatic Safety of Adjunctive High-Dose Melatonin in Participants Receiving Ocrelizumab for Primary Progressive Multiple Sclerosis: Liver Toxicity Findings from a Phase I/II Randomised Clinical Trial (MELATOMS-1). CNS Drugs. 2026. https://doi.org/10.1007/s40263-025-01261-w
  20. Sola E, Ramos E, Romero A, et al. Atrioventricular Block Potentially Associated with Melatonin Supplementation: A Case Report and Systematic Review of Cardiac Rhythm Adverse Events. Pharmaceuticals. 2026. https://doi.org/10.3390/ph19071069

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