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Melatonin (sleep)

Melatonin is a hormone that helps time the body clock, and melatonin supplements are most often made synthetically. Randomised trials show the clearest benefit for jet lag in air travellers crossing five or more time zones. For adults with long-standing sleep difficulties the effects are small and inconsistent: an older meta-analysis found sleep onset about 7 minutes faster, a 2022 meta-analysis found no significant effect in adults, and a 2017 sleep-medicine guideline suggests against it for chronic insomnia. Short-term use appears to be well tolerated in trials, long-term safety data are lacking, and the dose in over-the-counter products often differs from the label.

  • Sleep
  • Vegan

Evidence retrieved up to

What the research shows

In randomised trials of air travellers crossing five or more time zones, melatonin taken close to bedtime at the destination reduced jet-lag symptoms compared with placebo.

Moderate certaintyFurther research may change the size of the effect.
Take care: see the safety noteBenefit

Who this is about

adult air travellers crossing five or more time zones

Practical note

Graded moderate: nine of ten placebo-controlled trials agreed, with a large effect (number needed to treat 2), but the trials were small, the review dates from 2002, and NCCIH rates one sleep-quality outcome as low-quality evidence. The trials used 0.5 to 5 mg a day; doses above 5 mg appeared no more effective.

Vegan note

NCCIH notes that most melatonin supplements are made synthetically rather than from animals.

Safety note

The Cochrane review notes that taking melatonin at the wrong time of day can cause sleepiness and delay adaptation, and that case reports suggest possible harm in people with epilepsy and people taking warfarin.

Sources

In adults and children with primary sleep disorders, melatonin shortened the time to fall asleep by about 7 minutes and lengthened total sleep by about 8 minutes compared with placebo, effects the authors describe as modest; a later meta-analysis restricted to chronic insomnia found no significant effect in adults.

Low certaintyFurther research is likely to change this.
No known concerns at usual amountsUnclear

Who this is about

adults and children with primary sleep disorders

Practical note

Graded low: randomised trials, downgraded for inconsistency (the 2013 meta-analysis of 19 trials found small benefits, while the 2022 meta-analysis of 24 trials found no significant benefit in adults and some in children and adolescents) and for heterogeneity. A 2017 American Academy of Sleep Medicine guideline made a weak suggestion against melatonin for chronic insomnia in adults.

Sources

Laboratory analyses of over-the-counter melatonin products found that the melatonin content often differed widely from the label, and some products also contained serotonin.

Low certaintyFurther research is likely to change this.
Take care: see the safety noteRisk

Who this is about

people using over-the-counter melatonin supplements

Practical note

Graded low: product-testing studies of 31 supplements (2017) and 25 gummy products (2023, as summarised by NCCIH); findings may not apply to products regulated as medicines in other countries.

Vegan note

NCCIH notes that melatonin supplements can be made from animals or microorganisms but most often are synthetic.

Safety note

NCCIH reports rising numbers of accidental melatonin ingestions by young children, many involving flavoured products such as gummies.

Sources

In placebo-controlled trials lasting mostly four weeks or less, adverse events with melatonin were few and generally mild to moderate, most often daytime sleepiness, headache and dizziness; evidence on long-term use is scarce.

Low certaintyFurther research is likely to change this.
Take care: see the safety noteRisk

Who this is about

adults and children taking melatonin for sleep in trials

Practical note

Graded low: the adverse-event data come from 37 randomised trials, but most were short and only eight were rated good for risk of bias, so rare or long-term harms cannot be excluded. Trial doses ranged from 0.15 to 12 mg a day.

Safety note

NCCIH notes that people with epilepsy and people taking blood thinners need medical supervision when using melatonin, that safety in pregnancy and breastfeeding has not been studied, and that melatonin may stay active longer in older people and cause daytime drowsiness.

Sources

In randomised trials of adults with various health conditions, melatonin improved self-rated sleep quality on the Pittsburgh Sleep Quality Index compared with control, with results varying widely between studies.

Low certaintyFurther research is likely to change this.
No known concerns at usual amountsBenefit

Who this is about

adults with various health conditions

Practical note

Graded low: 23 randomised trials, downgraded for high heterogeneity (I2 80.7%) and indirectness (mixed populations with different underlying conditions). The pooled improvement was 1.24 points on the 21-point index.

Sources