Melatonin: what it can and can't do for sleep

Melatonin is a hormone your body makes that helps time sleep. ^[4][5] As a supplement, trials suggest it shortens the time to fall asleep by a few minutes on average, but a major medical guideline suggests against using it to treat chronic insomnia. ^[1][2] It looks more useful for some body-clock problems, such as jet lag, than for ordinary insomnia. ^[3][4]

What the research says

The trials show a small effect on falling asleep and little else. A 2013 meta-analysis of 19 placebo-controlled studies in primary sleep disorders (1,683 adults and children) found melatonin shortened the time to fall asleep by about 7 minutes and lengthened total sleep by about 8 minutes, with slightly better sleep quality, effects the authors called modest. ^[1] A second meta-analysis of 12 trials found the best evidence was for falling asleep faster in primary insomnia and in delayed sleep phase syndrome (a body clock that runs late), and for steadying the sleep-wake pattern in people who are blind. ^[3] The American Academy of Sleep Medicine, working from three short trials in adults over 55, suggests clinicians not use melatonin for chronic insomnia, a weak recommendation on evidence it calls minimal. ^[2] For jet lag, nine of ten trials found it reduced symptoms after flights across five or more time zones. ^[4] In plain terms, melatonin shifts sleep onset by minutes and helps most where the body clock is out of step.

The studies behind this

• Meta-analysis (Ferracioli-Oda, 2013): 19 randomised, placebo-controlled studies of adults and children with primary sleep disorders (1,683 people). Melatonin shortened the time to fall asleep by about 7 minutes and increased total sleep time by about 8 minutes compared with placebo. Overall sleep quality improved slightly. The authors called the effects modest and smaller than other drug treatments for insomnia. ^[1]
• Second meta-analysis (Auld, 2017): 12 randomised trials. The most convincing evidence was for shorter time to fall asleep in primary insomnia and delayed sleep phase syndrome (a body clock that runs late), and for regulating the sleep-wake pattern in people who are blind. The authors called for larger trials. ^[3]
• American Academy of Sleep Medicine guideline (2017): a weak recommendation that clinicians not use melatonin to treat sleep-onset or sleep-maintenance insomnia in adults. It rests on three short trials, all in adults over 55, and the guideline describes the available evidence as minimal and weakly against benefit. ^[2]
• Jet lag (Cochrane review, 2002): nine of ten trials found melatonin reduced jet lag after flights across five or more time zones. ^[4]

Does "weak recommendation against" mean it does nothing?

No. The guideline's authors based their recommendation on limited evidence and judged the benefits and harms to be roughly equal. They also expected that most well-informed patients would still choose melatonin over no treatment, because it is easy to get and widely seen as a benign sleep aid. ^[2] "Not recommended on thin evidence" is different from "proven not to work". The meta-analyses above found small average benefits, and an average hides people who respond more or less. ^[1][3] The same guideline weighs prescription sleep medicines in the same cautious way; see CBT-I versus sleeping pills.

Why melatonin is not like most sleep problems

Melatonin is described as a hormone that helps regulate the body's rhythms. ^[4][5] That helps explain why the evidence looks stronger for conditions where the clock itself is misaligned, such as jet lag or a late-running clock, than for insomnia driven by worry and habits. ^[3][4] That explanation is our interpretation of the pattern across the studies. No single trial tested it. Night-shift work is another clock problem, with its own research; see napping before a night shift.

What is in the bottle?

Melatonin sold as a supplement can differ from its label. In a Canadian laboratory analysis of about 30 commercial products, measured melatonin ranged from 83% below to 478% above the label. Batches of the same product varied by as much as 465%. More than 71% were not within 10% of their label, and about a quarter contained serotonin, a related chemical. ^[5] The study did not name brands or say how common this is across everything on shelves today.

What does Health Canada say?

Health Canada's notice of 26 May 2026 states that all currently licensed melatonin natural health products are indicated for adult use only, and that none is authorised for children or adolescents. From 2 June 2026 it changes the Prescription Drug List so that melatonin for sleep-related use in people under 18 is a prescription drug. Its reasons: a clinician should rule out underlying causes of a child's sleep problems, guide the family on sleep habits first, and reduce the risk of harm to children and adolescents. ^[6]

Safety and who should check first

• Ask your doctor or pharmacist before taking it, especially if you take other medicines. The Cochrane jet-lag review notes that case reports suggested people with epilepsy, and people taking warfarin (a blood thinner), could be harmed. ^[4]
• Children and teens: talk to a doctor first. ^[6]
• Pregnancy and breastfeeding: we did not find a source we could verify for this article, so please ask your doctor or pharmacist.
• This article gives no amounts or timing, because the right choice depends on you and your other medicines.

Where the evidence is thin

• The trials were small, short, and varied in design. ^[1][3]
• The strongest results concern falling asleep, not staying asleep. ^[3]
• The Cochrane authors noted that the pharmacology and toxicology of melatonin need systematic study. ^[4]
• Product testing covered a limited number of products at one point in time. ^[5]

Where does this leave you?

If sleep problems have lasted months, the first-line treatment in major guidelines is CBT-I (cognitive behavioural therapy for insomnia), not a supplement. Small Hours turns a nightly sleep diary into a six-week CBT-I program built around your own sleep. You can sign up at trysmallhours.com.

When should you talk to a doctor?

• Before starting melatonin, especially with other medicines, a health condition, pregnancy or a child.
• Sleep trouble lasting months, or loud snoring and breathing pauses.
• Low mood or anxiety that comes with poor sleep.

General education, not medical advice.