A summary of published research, not medical advice. See the Disclaimer.
Studies: every indexed trial and review on this topic, scored
Melatonin is a hormone the pineal gland releases in darkness, sold as an oral supplement in many countries.
Best-supported effect: Shorter time to fall asleep in adults and children with primary sleep disorders. Probably helps a little (moderate evidence).
Most-cited weak claim: Clinically meaningful relief of chronic insomnia. May make little or no difference (weak evidence).
How we grade evidence · Last reviewed: October 2026
What you need to know
In adults and children with primary sleep disorders, melatonin shortened the time to fall asleep a little, with moderate evidence. It moved sleep timing earlier in delayed sleep phase disorder and reduced jet lag after flights crossing 5 or more time zones, both with moderate evidence. For relief of chronic insomnia and for sleep in dementia, it made little or no difference, with weak evidence. Adverse reactions such as headache, dizziness, nausea and daytime sleepiness were reported in 9.5% of people on prolonged-release products against 7.4% on placebo. With fluvoxamine, melatonin exposure rose 17-fold. In an analysis of 31 supplements, melatonin content ranged from 83% below to 478% above the label. Jet lag trials used 0.5 to 5 mg a day near the target bedtime at the destination.
| Effect | Verdict | What was measured | Studied in |
|---|---|---|---|
| Shorter time to fall asleep | Probably helps a little (moderate evidence) Pooled analysis of 19 trials in 1,683 people, about 7 minutes faster, size varied between trials |
Measured | Adults and children with primary sleep disorders |
| Earlier sleep timing | Probably helps (moderate evidence) Few, small trials in people whose body clock runs late |
Measured | Adults and children with delayed sleep phase disorder |
| Less jet lag after eastward or long flights | Probably helps (moderate evidence) Cochrane review of 10 trials, 9 showing less jet lag |
Self-reported | Air travellers crossing 5 or more time zones |
Time to fall asleep. A meta-analysis of 19 trials with 1,683 participants found that melatonin cut the time to fall asleep by about 7 minutes and added about 8 minutes of total sleep compared with placebo [1]. An earlier meta-analysis found a reduction of about 12 minutes across primary sleep disorders [2]. The size of the effect varied between trials (I² = 56%), and some results came from sleep diaries [1]. Probably helps a little (moderate evidence): downgraded because results varied between trials. The effect is small in absolute terms.
Sleep timing in delayed sleep phase disorder. In people whose body clock runs late, melatonin cut the time to fall asleep by about 39 minutes, based on 2 trials [2]. A second meta-analysis of 9 trials found that the body's own melatonin rise shifted about 1.2 hours earlier and sleep onset about 40 minutes earlier [3]. Probably helps (moderate evidence): downgraded because the trials were few and small.
Jet lag. In a Cochrane review, 9 of 10 trials found less jet lag after flights crossing 5 or more time zones when travellers used melatonin close to the target bedtime at their destination [4]. The benefit was likely larger when more time zones were crossed and smaller on westward flights [4]. Probably helps (moderate evidence): downgraded because the review included only 10 trials, one of which could not be used.
| Effect | Verdict | What was measured | Studied in |
|---|---|---|---|
| Clinically meaningful relief of chronic insomnia | May make little or no difference (weak evidence) Pooled analysis comparing insomnia drugs in adults, no meaningful overall benefit |
Self-reported | Adults with insomnia disorder |
| Better sleep in dementia | May make little or no difference (weak evidence) Cochrane review in Alzheimer's disease, certainty rated low |
Measured | Adults with Alzheimer's disease and sleep disturbances |
More on this result under Claimed but unsupported or contested.
Chronic insomnia. A network meta-analysis compared drug treatments for insomnia disorder in adults. Melatonin showed no overall material benefit, and several hypnotics worked better than melatonin for acute treatment [5]. Sleep onset comes a few minutes sooner with melatonin, which is not enough to change insomnia as a disorder. The claim mostly comes from extending that small effect. May make little or no difference (weak evidence): the review rated its certainty for the melatonin comparisons between moderate and very low.
Dementia. A Cochrane review found that melatonin doses up to 10 mg may make little or no difference to total sleep time or night waking over 8 to 10 weeks in people with Alzheimer's disease [6]. The review rated its certainty as low.
No trials have tested nightly use over several years, in any population.
Shown in humans
Shown only in animals or cells
Theory only
| Side effect | Verdict | How often vs placebo | Source | Studied in |
|---|---|---|---|---|
| Any adverse reaction (headache, dizziness, nausea, daytime sleepiness) | Probably happens (moderate evidence) Slow-release trials, 9.5% on product against 7.4% on placebo |
9.5% vs 7.4% (prolonged-release product trials) | [2][7][10][11] | |
| Daytime sleepiness | May happen (weak evidence) Reported in 1.66% of trial participants, no placebo comparison given |
1.66% of trial participants; placebo rate not reported | [10][11] | |
| Hypothermia | May happen (weak evidence) 0.62% of trial participants in one formal review of studies, no placebo rate |
0.62% of trial participants; placebo rate not reported | [11] | |
| Seizures in people with epilepsy | Unknown (very weak evidence) Reports of single patients only, not studied in people with epilepsy |
Case reports only | [4] | People with epilepsy |
| Serious harm after accidental ingestion by children | Unknown (very weak evidence) Poison center tracking data, cause of each outcome unconfirmed |
Not reported (surveillance data) | [8] | Children |
Short-term data come from adults. Most trials lasted under 3 months, so the short-term grade does not extend to long-term use [2][11]. United States poison center reports of melatonin ingestion by children rose 530% between 2012 and 2021; 5 children needed mechanical ventilation and 2 died, though surveillance data cannot confirm the cause of each outcome [8].
This lists what studies and labels report. A pharmacist or prescriber can say whether it applies to a specific person.
This lists what studies and labels report. A pharmacist or prescriber can say whether it applies to a specific person.
| Combined with | What happened | Verdict | Source | Studied in |
|---|---|---|---|---|
| Fluvoxamine | Melatonin exposure rose 17-fold (AUC) and peak level 12-fold; the label states "The combination should be avoided." | May happen (weak evidence) Drug label data only, melatonin blood exposure rose 17-fold |
[10] | |
| Zolpidem | In a trial, taking both worsened attention, memory and coordination one hour after dosing compared with zolpidem alone | May happen (weak evidence) Trial in the drug label, attention, memory and coordination worsened |
[10] | |
| Other benzodiazepines and sleeping pills (zaleplon, zopiclone) | The label states melatonin may add to their sedative effect | Unknown (very weak evidence) Statement on the drug label only, no trial described for these drugs |
[10] | |
| Imipramine | No relevant change in blood levels in a co-administration study; people felt more tranquil and had more difficulty performing tasks than with imipramine alone | May happen (weak evidence) One study of taking both together, more task difficulty without relevant blood level change |
[10] | |
| Thioridazine | No relevant change in blood levels in a co-administration study; people reported more "muzzy-headedness" than with thioridazine alone | May happen (weak evidence) One study of taking both together, more muzzy-headedness without relevant blood level change |
[10] | |
| Alcohol | The label states alcohol reduces melatonin's effect on sleep | Unknown (very weak evidence) Statement on the drug label only, no study data described |
[10] | |
| Oestrogens (contraceptives, hormone replacement) | The label states they raise melatonin levels by slowing its breakdown | Unknown (very weak evidence) Statement on the drug label only, no measured rise in levels given |
[10] | |
| Cimetidine, 5- or 8-methoxypsoralen, quinolone antibiotics | The label states they raise melatonin levels by slowing its breakdown | Unknown (very weak evidence) Statement on the drug label only, size of rise not given |
[10] | |
| Carbamazepine, rifampicin, cigarette smoking | The label states they may lower melatonin levels by speeding its breakdown | Unknown (very weak evidence) Statement on the drug label only, size of drop not given |
[10] | |
| Warfarin | Case reports describe possible harm | Unknown (very weak evidence) Reports of single patients only, people on blood thinners not studied |
[4] |
The label also notes that melatonin induced the liver enzyme CYP3A in lab tests at concentrations above therapeutic levels; whether this lowers levels of other drugs in people is unknown [10].
These are the amounts used in the studies. They are not recommendations.
Jet lag trials used daily doses of 0.5–5 mg near the target bedtime at the destination. The doses worked about equally well, though 5 mg brought faster sleep onset and better sleep than 0.5 mg, and doses above 5 mg appeared no more effective [4]. Trials in delayed sleep phase disorder compared melatonin with placebo in 91 adults and 226 children [3]. Dementia trials used doses up to 10 mg [6].
Retail products did not always match what trials used. In an analysis of 31 supplements, melatonin content ranged from 83% below to 478% above the label, and 26% of products contained serotonin [9].