Does melatonin work for sleep?

What is melatonin?

Melatonin is the hormone your brain produces in response to darkness. It helps time the body’s 24-hour rhythms, and light at night can block its production (NCCIH, 2024). It is less a sleeping pill than a message: night has started.

That message is timed by light. Morning light sets the clock that decides when the evening rise comes (light is the clock), and the clock runs separately from the pressure to sleep that builds the longer you are awake (two processes decide when you are sleepy). A tablet adds to the signal. Whether that helps depends on whether the signal was the problem.

Does melatonin help you fall asleep?

A little. A 2013 meta-analysis combined 19 placebo-controlled trials in 1,683 adults and children with sleep disorders — 14 trials in insomnia, 4 in a delayed body clock and 1 in a REM sleep disorder — at doses from 0.1 to 5 mg (Ferracioli-Oda and colleagues, 2013).

On average, people taking melatonin fell asleep 7 minutes sooner and slept 8 minutes longer than on placebo, and rated their sleep slightly better. Longer trials and higher doses showed larger effects, and the benefit did not fade with continued use. The authors call the effects modest, and smaller than those of other insomnia medicines.

Seven minutes is real. It is also less than most people hope for when they open the bottle.

Should you take melatonin for insomnia?

For chronic insomnia in adults, the American Academy of Sleep Medicine suggests that clinicians not use melatonin, whether the trouble is falling asleep or staying asleep — a weak recommendation, which reflects thin evidence rather than proof of no effect (Sateia and colleagues, 2017). NCCIH likewise finds not enough strong evidence on its effectiveness or safety for chronic insomnia (2024).

In the UK, melatonin is prescription-only, and it is mainly used for short-term sleep problems in people aged 55 and over (NHS, 2023).

For insomnia that has lasted months, the recommended first treatment is cognitive behavioural therapy for insomnia, CBT-I (Qaseem and colleagues, 2016; Edinger and colleagues, 2021). How melatonin compares with magnesium, valerian and the rest is on sleep supplements: what the evidence shows.

Does melatonin help with jet lag?

Yes — this is where its evidence is strongest. A Cochrane review of 10 trials in airline passengers, airline staff and military personnel found that in 9 of them, melatonin taken close to the target bedtime at the destination (10 pm to midnight) reduced jet lag after flights crossing 5 or more time zones (Herxheimer and Petrie, 2002).

• Doses from 0.5 to 5 mg worked about equally well, though people fell asleep faster and slept better on 5 mg than on 0.5 mg. Above 5 mg was no better.
• A 2 mg slow-release form did relatively poorly, which the authors took to mean that a short, high peak works better.
• The benefit was larger the more time zones were crossed, and smaller flying west.
• Timing mattered: taken at the wrong time, early in the day, melatonin caused sleepiness and slowed adjustment to local time.

The review was last updated in 2002. Daylight at the destination does the rest of the work — see light is the clock.

Those are the doses and timings the trials used, not advice for you: a pharmacist or doctor can say whether melatonin suits you, and what it interacts with.

What if your body clock runs late?

Some people’s clocks run hours behind the day: bedtime arrives before the clock is ready, and mornings are a struggle. Tired but can’t sleep explains why a late clock feels like being tired and wired at once. When it is persistent, sleep doctors call it delayed sleep–wake phase disorder, and it is the other place melatonin has a recommendation behind it.

The American Academy of Sleep Medicine suggests strategically timed melatonin for it — a second-tier, weak recommendation — and also for blind adults whose clocks drift, and for children and adolescents with irregular sleep–wake rhythms and neurological conditions (Auger and colleagues, 2015).

The word that matters is timed. Taken a few hours before your own melatonin would rise, it pulls the clock earlier; taken soon after waking, it pushes it later (Burgess and colleagues, 2010). This is a diagnosis to make with a sleep specialist, not a guess to make with a bottle.

Does timing matter more than dose?

For moving the clock, it does. In a 2010 laboratory study, 34 healthy adults aged 18 to 42 took 0.5 mg of melatonin or a placebo at the same clock time for 3 days, and the researchers compared the result with an identical earlier study of 3 mg (Burgess and colleagues, 2010).

• 0.5 mg moved the clock earlier most when taken in the afternoon, 2 to 4 hours before the body’s own evening melatonin began.
• The best time for the smaller dose was later than for the larger one.
• Each taken at its best time, the two doses shifted the clock by similar amounts.

That is why “how much melatonin should I take?” has no single answer. The 19 trials pooled in 2013 used 0.1 to 5 mg, and in the jet-lag trials nothing above 5 mg added anything. Choosing a dose and a time is a conversation for a doctor or pharmacist, not something a page can settle.

Is the dose on the label the dose in the bottle?

Not reliably. In the US, melatonin is sold as a dietary supplement and, as the American Academy of Sleep Medicine puts it, is “not under FDA oversight like other” over-the-counter or prescription drugs (2022). When researchers have measured the contents:

• 31 supplements tested in 2017 held anywhere from about a sixth of the stated melatonin to nearly six times it, batches of the same product differed widely, and 8 contained serotonin (Erland and Saxena, 2017). The most variable, the AASM notes, were chewable tablets — the form children are most likely to use.
• Of 25 melatonin gummy products sold in the US, studied in 2023, 3 contained within a tenth of the labelled amount; a serving held anywhere from 1.3 to 13.1 mg (Cohen and colleagues, 2023).

A label that says 1 mg may not mean 1 mg, and that matters most for a child.

Is melatonin safe for children?

Only with a health professional’s advice. The American Academy of Sleep Medicine advises parents to talk to one before giving melatonin or any supplement to a child, says many sleep problems are better managed by changing schedules, habits or behaviour, and asks that melatonin be kept out of children’s reach like any other medicine (2022). In the UK, specialists sometimes prescribe it for children with longer-term sleep problems (NHS, 2023).

The reason for that last request: from 2012 to 2021, US poison centres recorded 260,435 melatonin ingestions in people aged 19 or under, and the yearly number rose more than sixfold. Of the children seen at a hospital or clinic, 4,097 were admitted and 287 needed intensive care; 5 needed a ventilator to breathe, and 2 died, both under the age of 2 (Lelak and colleagues, 2022).

What are melatonin’s side effects, and who should avoid it?

Short-term use appears to be safe for most people. The side effects reported are mostly mild — headache, dizziness, nausea and sleepiness — and the long-term effects are unclear (NCCIH, 2024). Ask a doctor or pharmacist before taking it if any of these apply:

• Pregnancy. The NHS does not usually recommend it, because little is known about its effect on babies.
• Other medicines. The NHS lists, among others, warfarin, the antidepressants fluvoxamine and amitriptyline, the epilepsy drug carbamazepine, blood-pressure medicines, oestrogens in contraceptives and HRT, and sleeping pills such as zolpidem and zopiclone. NCCIH adds that people with epilepsy and people taking blood thinners need medical supervision.
• Liver or kidney problems, or an autoimmune condition such as rheumatoid arthritis, multiple sclerosis or lupus (NHS).
• Dementia. The American Academy of Sleep Medicine recommends against melatonin for older people with dementia (Auger and colleagues, 2015).
• Needing to stay alert. France’s food-safety agency advises people whose activities require sustained alertness to avoid melatonin supplements (ANSES, 2018). The NHS says not to drive if it makes you sleepy, and to avoid alcohol while taking it.

Can you buy melatonin over the counter?

It depends on where you live.

• United States: yes, as a dietary supplement (NCCIH, 2024).
• United Kingdom: no. It is a prescription-only medicine; the NHS says supplements sold in other countries are not authorised for sale in the UK, and advises against ordering melatonin online (NHS, 2023).
• European Union: it varies. France’s food-safety agency noted in 2018 that melatonin’s status and limits differ across the EU; France itself allowed food supplements providing less than 2 mg a day (ANSES, 2018).
• Elsewhere: in several other countries, melatonin is available only on prescription (NCCIH, 2024).

Wherever you buy it, what is in the bottle may not match the label.