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Also known as N-acetyl-5-methoxytryptamine
Hormone released by the pineal gland in response to darkness that signals circadian phase to the brain's suprachiasmatic nucleus; low-dose supplementation can shorten time to fall asleep and ease jet lag.
We link to relevant studies and leave interpretation to you and your healthcare professional.
Number of audited published findings for Melatonin by condition. Drill into a pair page for the full breakdown.
Where people report using it and what trials suggest
Common claims the trials do not support
Hormone signalling darkness to the body clock. Best evidence is for circadian problems (jet lag, delayed sleep phase) rather than generic insomnia.
Safety notes: Physiological doses (0.3-1 mg) often outperform megadoses. Morning grogginess at high doses. Not for unsupervised paediatric chronic use.
Evidence grades reflect study quality and consistency, not marketing claims.
Summaries of published trial results for this compound, grouped by condition. Numbers are reported exactly as the researchers published them — we never calculate or convert.
How to read this table
In short: benefit is what was observed; evidence is how much you should trust the observation. A “Benefit seen” tag on a weak study counts for far less than the same tag on a meta-analysis.
| Outcome measured | What trials found | Effect size | People studied | Duration | Type of evidence | Study |
|---|---|---|---|---|---|---|
| adverse effects | It is unclear if oral melatonin causes adverse effects compared to no treatment in 11 randomized trials, though they would probably be mild.Unclear | no number reported | 11 | — | Meta-analysis · 2015 | PMID 26731279 |
| symptoms associated with jet lag syndrome | Oral melatonin probably reduces jet lag symptoms compared to no treatment in 11 randomized trials.Benefit seen | no number reported | 11 | — | Meta-analysis · 2015 | PMID 26731279 |
| Dose-response of melatonin above 5mg versus 0.5-5mg | Melatonin doses above 5mg were no more effective than doses between 0.5 and 5mg compared head-to-head. |
Associated conditions and community-reported outcomes, wrapped together on one page. Aggregates appear only once enough reports arrive.
How this compound is sold in the UK, and where our readers typically find it.
Prescription-only in the UK
Melatonincan't legally be sold over the counter here. It's available only with a prescription, through a consultation with a doctor or qualified prescriber. We don't sell medicines and never will — our job is the evidence, not the dispensing.
How prescription-only compounds work →| no number reported |
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| Systematic review · 2002 |
| PMID 12076414 |
| Jet lag symptoms after crossing five or more time zones | Melatonin significantly reduced jet lag after crossing five or more time zones compared with placebo (NNT = 2).Benefit seen | 2 NNT | — | — | Systematic review · 2002 | PMID 12076414 |
| Dose-response of melatonin above 5mg versus 0.5-5mg | Melatonin doses above 5mg were no more effective than doses between 0.5 and 5mg compared head-to-head.No clear benefit | no number reported | — | — | Systematic review · 2001 | PMID 11279722 |
| Jet lag symptoms after crossing five or more time zones | Melatonin significantly reduced jet lag after crossing five or more time zones compared with placebo (NNT = 2).Benefit seen | 2 NNT | — | — | Systematic review · 2001 | PMID 11279722 |
| Circadian phase advance with combined treatment | Melatonin plus light advanced circadian timing by 1.04 h compared to pretreatment timing. (p<0.0002)Benefit seen | 1.04 h | 11 | — | RCT · 2011 | PMID 21069516 |
| Circadian phase advance with light | Light treatment produced a nonsignificant 0.31 h circadian advance compared to pretreatment timing.No clear benefit | 0.31 h | 11 | — | RCT · 2011 | PMID 21069516 |
| Circadian phase advance with melatonin | Melatonin advanced circadian timing by 0.72 h compared to pretreatment timing. (p<0.005)Benefit seen | 0.72 h | 11 | — | RCT · 2011 | PMID 21069516 |
| Outcome measured | What trials found | Effect size | People studied | Duration | Type of evidence | Study |
|---|---|---|---|---|---|---|
| sleep duration | Melatonin increased sleep duration by 44 min compared with placebo in children with ASD. (Hedge's g 1.07 [95% CI 0.49-1.65])Benefit seen | 44 min | — | — | Meta-analysis · 2020 | PMID 32112261 |
| sleep efficiency | Behavioral interventions improved sleep efficiency by 5.59 compared to control in children with ASD. (95% CI 0.87-10.31, P=0.02)Benefit seen | 5.59 | — | — | Meta-analysis · 2020 | PMID 32112261 |
| sleep-onset latency | Behavioral interventions decreased sleep-onset latency by 18.31 min compared to control in children with ASD. (95% CI -30.84 to -5.77, P=0.004)Benefit seen | -18.31 min | — | — | Meta-analysis · 2020 | PMID 32112261 |
| sleep-onset latency | Melatonin decreased sleep-onset latency by 39 min compared with placebo in children with ASD. (Hedge's g -2.46 [95% CI -1.96 to -2.98])Benefit seen | 39 min | — | — | Meta-analysis · 2020 | PMID 32112261 |
| total sleep time | Behavioral interventions increased total sleep time by 24.41 min compared to control in children with ASD. (95% CI 5.71-43.11, P=0.01)Benefit seen | 24.41 min | — | — | Meta-analysis · 2020 | PMID 32112261 |
| cognitive outcomes | Limited studies suggested improvements in cognitive outcomes compared to no melatonin over 2 weeks to 12 months.Benefit seen | no number reported | — | 2 weeks and 12 months | Systematic review · 2023 | PMID 37429996 |
| fatigue | Limited studies suggested improvements in fatigue compared to no melatonin over 2 weeks to 12 months.Benefit seen | no number reported | — | 2 weeks and 12 months | Systematic review · 2023 | PMID 37429996 |
| safety | No substantial safety issues were found with melatonin compared to no melatonin over 2 weeks to 12 months.No clear benefit | no number reported | — | 2 weeks and 12 months | Systematic review · 2023 | PMID 37429996 |
| sleep conditions | Limited studies suggested improvements in sleep conditions compared to no melatonin over 2 weeks to 12 months.Benefit seen | no number reported | — | 2 weeks and 12 months | Systematic review · 2023 | PMID 37429996 |