Melatonin for Sleep: Does It Work, Dosage and How to Get It in the UK
An honest look at what melatonin does, who it genuinely helps, and what the UK licensing means for you.
Part of our Sleep condition guide.
In short: Melatonin is a hormone that signals to your body that it is time to sleep. As a medicine it can help with short-term sleep problems — in the UK, prolonged-release melatonin is licensed for adults aged 55 and over. It works best alongside good sleep habits rather than instead of them, and it is prescription-only here.
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View Sleep Treatments →What melatonin is and what it actually does
Melatonin is a hormone produced by the pineal gland in your brain. Its release is controlled by light: levels stay low through the day, begin rising a couple of hours before your usual bedtime, peak in the middle of the night, and fall again towards morning.
That rising signal is not what puts you to sleep. It is what tells the rest of your body that night has begun — body temperature drops, alertness fades, and the systems that keep you awake start standing down. Melatonin is the messenger, not the sedative.
This distinction explains almost everything else on this page. A sleeping tablet such as zopiclone works by suppressing the brain's arousal systems — it makes you sleepy regardless of what time it is. Melatonin works by telling your body what time it is. If your problem is that your body clock is running on the wrong schedule, that is powerful. If your problem is a racing mind at 2am, it is much less so.
Clinicians call this class of drug a chronobiotic: something that shifts the timing of the body clock. That is why melatonin's UK licences are for jet lag and for age-related sleep problems, rather than for insomnia in general.
Does melatonin work? An honest answer
Yes, but the size of the effect is smaller than the internet suggests, and it depends heavily on why you are not sleeping.
Pooled analyses of melatonin trials in people with primary sleep problems have generally found that it helps people fall asleep somewhat faster and sleep somewhat longer — but the average improvements are measured in single-digit minutes, not hours. That is a real effect, and it is statistically robust across studies. It is also not the transformation that a bottle of American gummies implies.
Two things make that average misleading in both directions:
- Averages hide responders. A modest mean improvement can be made up of some people who benefit substantially and others who notice nothing at all. Which group you fall into depends largely on whether your sleep problem is a timing problem
- Sleep quality is not just duration. The trials behind prolonged-release melatonin's UK licence looked at sleep quality and next-morning alertness in older adults, not only at minutes of sleep — and that is the outcome most people actually care about
The reason the licence stops at 55 is not arbitrary. Melatonin secretion falls as people get older, so a sleep problem in an older adult is more likely to involve a genuine shortfall in the signal. Topping up a hormone you are short of is a more plausible mechanism than topping up one you already have plenty of.
Who it helps most — and least
| Situation | Is melatonin likely to help? |
|---|---|
| Jet lag after crossing time zones | Yes — this is a pure timing problem and it is a UK licensed indication. Timing of the dose matters more than the dose itself |
| Poor sleep quality, aged 55 or over | Yes — the licensed indication for prolonged-release melatonin, where declining natural production is part of the picture |
| Body clock running late (falling asleep at 3am, unable to wake for work) | Often — a timing problem, though it needs careful dose timing and is not a licensed use in adults |
| Shift work disrupting your sleep schedule | Sometimes — again a timing problem, but the shifting schedule makes it harder to get right |
| Lying awake with a racing mind or anxiety | Unlikely — this is an arousal problem, not a timing problem. CBT-I addresses it far more effectively |
| Waking repeatedly because of pain, reflux, or needing the toilet | No — treat the underlying cause; melatonin will not touch it |
If your row in that table says "unlikely" or "no", melatonin is not the answer, and no dose adjustment will make it one. That is a more useful thing to know than a list of doses.
Melatonin dosage in the UK
UK licensed melatonin comes in two strengths, and each belongs to a specific use.
| Product | Dose | When to take it | How long |
|---|---|---|---|
| Prolonged-release melatonin 2mg (Circadin and generics) | One 2mg tablet daily | 1–2 hours before bedtime, after food. Swallow whole | Up to 13 weeks |
| Immediate-release melatonin 3mg | One 3mg tablet daily, increased to 6mg only if 3mg is insufficient | At your normal bedtime in the destination time zone, on arrival. Never before 8pm or after 4am local time | Up to 5 days per trip |
More is not better. American products commonly sell 5mg and 10mg doses, and a great deal of online advice is written around them. Higher doses push melatonin levels well above anything the body produces naturally, and the main things that reliably increase with dose are next-day grogginess and headache — not sleep. UK licensed doses are 2mg and 3mg for good reason.
The prolonged-release tablet must be swallowed whole. Breaking, crushing or chewing it destroys the mechanism that releases the melatonin slowly, turning a night-long release into an immediate one — which is a different medicine for a different purpose.
How long it takes to work
Two different questions get muddled here.
How long until it is in your system? Immediate-release melatonin is absorbed quickly, with blood levels peaking within about an hour — which is why jet-lag dosing is tied so tightly to bedtime. The prolonged-release tablet is deliberately slower, which is why it is taken one to two hours before bed rather than as you get into it.
How long until you notice a difference in your sleep? Honestly, this varies, and the patient information leaflet for Circadin does not commit to a timeline. Some people notice something on the first night; for others the benefit builds over the first week or two of regular use. Melatonin is not a knockout drop, so if you are waiting to feel yourself being switched off, you may conclude it has failed when it has not.
What matters more than either is consistency. Taking it at the same time each night reinforces the timing signal. Taking it at wildly different times sends a confusing one.
Immediate-release or prolonged-release?
For a sleep problem that is not travel-related, prolonged-release is almost always the relevant formulation. The reason is what each one does across the night.
Immediate-release
A sharp peak soon after taking it, then a fall. Good at shifting the clock — the licensed use is jet lag. Poor at holding sleep together at 4am, because it is long gone by then.
Prolonged-release
A slow release across the night, closer to the body's own overnight profile. Licensed for short-term insomnia in adults 55 and over, and the better fit for staying asleep.
If you wake at three or four in the morning and cannot get back to sleep, immediate-release melatonin is unlikely to help you, whatever dose you take. Our full comparison of melatonin vs Circadin works through the decision in detail.
Insomnia, 55+
Circadin 2mg Prolonged-Release
The original prolonged-release melatonin brand. Licensed for short-term primary insomnia in adults aged 55 and over.
View treatment →Lower-cost generic
Melatonin 2mg Modified Release
The same active ingredient and strength as Circadin in a generic prolonged-release tablet.
View treatment →Side effects and who should avoid it
Melatonin is generally well tolerated at UK licensed doses. The effects reported most often are drowsiness, headache and dizziness. Less commonly people report irritability, restlessness, vivid dreams or nightmares, and — unhelpfully — occasionally insomnia itself.
Do not drive after taking melatonin. It causes drowsiness and reduced alertness, and the licensed products carry an explicit warning about driving and operating machinery. If drowsiness carries over into the following day, speak to your prescriber.
Melatonin is not recommended, or needs specific advice first, if any of these apply to you:
- You are under 18 — the adult products are not licensed for children or adolescents
- You are pregnant or breastfeeding — melatonin crosses the placenta and passes into breast milk
- You have an autoimmune condition — melatonin is not recommended, as it has immune-modulating effects
- You have moderate or severe liver impairment — melatonin is cleared by the liver and levels can rise considerably
- You have epilepsy — melatonin may affect seizure frequency and this needs discussing with the team managing it
- You take fluvoxamine — this combination should be avoided; fluvoxamine can raise melatonin levels many times over
- You take warfarin or another anticoagulant — melatonin may affect anticoagulant activity
- You take a benzodiazepine or a Z-drug — the sedative effects add together
Alcohol deserves its own line: it reduces melatonin's effect on sleep, and independently fragments sleep in the second half of the night. A nightcap and a melatonin tablet work against each other.
The things that work better than melatonin
For insomnia that has lasted more than a few weeks, the most effective treatment is not a tablet. UK guidance puts cognitive behavioural therapy for insomnia (CBT-I) first, and the evidence for it is stronger than for any sleep medication — particularly because its benefits persist after the treatment ends, which is not true of hypnotics.
CBT-I is not a relaxation programme. It works on the specific mechanisms that keep insomnia going: the hours spent lying awake in bed, the compensatory lie-ins, the clock-watching, and the anxiety about not sleeping that itself prevents sleep. Digital CBT-I courses are available, and some are commissioned within the NHS.
Underneath that sit the habits that make any sleep treatment more likely to work:
1
Anchor your wake time, not your bedtime
Getting up at the same time every day, weekends included, does more to stabilise a body clock than going to bed at the same time. Bedtime follows sleepiness; wake time sets the schedule.
2
Get daylight early
Light in the first hour or two after waking is the strongest single input to your circadian system. It also brings forward the time your own melatonin starts rising that evening.
3
Do not lie awake in bed
If you have been awake for a while and are not drowsy, get up and do something undemanding in dim light. Returning to bed only when sleepy rebuilds the association between bed and sleep.
4
Deal with caffeine and alcohol honestly
Caffeine has a long half-life and an afternoon coffee is still working at midnight for many people. Alcohol shortens the time to fall asleep and then wrecks the second half of the night.
How to get melatonin in the UK
Melatonin is a prescription-only medicine in the UK, so it cannot be bought over the counter in a pharmacy, supermarket or health-food shop. This catches many people out, because it is sold openly as a supplement in the United States and much of the advice online is written for that market. Our guide to whether you can buy melatonin over the counter in the UK covers the law and the import risks in full.
Legally, there are two routes: a prescription from your NHS GP, or a consultation with a regulated online pharmacy where a registered prescriber reviews your case and issues a prescription only if melatonin is appropriate for you. Both involve an assessment, because that assessment is the point.
Find Out Whether Melatonin Suits Your Situation
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Start a Sleep Consultation →Frequently Asked Questions
Does melatonin help you sleep?
It can, but the effect is more modest than most online advice suggests and it depends on why you are not sleeping. Melatonin is a timing signal rather than a sedative, so it helps most when the problem is that your body clock is running on the wrong schedule, such as jet lag, or when natural melatonin production has declined with age. Pooled trial data in people with primary sleep problems shows people fall asleep somewhat faster and sleep somewhat longer, with average improvements measured in single-digit minutes. If you are lying awake with a racing mind, melatonin is unlikely to be the answer and cognitive behavioural therapy for insomnia is considerably more effective.
What is the right melatonin dose for adults in the UK?
UK licensed melatonin comes in two strengths, each tied to a specific use. Prolonged-release melatonin is 2mg, taken as one tablet one to two hours before bedtime after food, and is licensed for short-term primary insomnia in adults aged 55 and over. Immediate-release melatonin is 3mg, taken at bedtime in the destination time zone for jet lag, increasing to 6mg only if 3mg is insufficient. The 5mg and 10mg doses sold in the United States are supplement doses, not UK licensed doses, and higher amounts mainly increase next-day grogginess and headache rather than improving sleep.
Is melatonin addictive?
Melatonin is not considered addictive in the way that benzodiazepines or Z-drugs can be. The patient information leaflet for Circadin states that there are no known harmful effects if treatment is interrupted or ended early, and that its use is not known to cause withdrawal effects after treatment completion. What some people do experience is a psychological reliance, where they feel unable to attempt sleep without taking something. That is one reason melatonin is licensed for short-term use with a defined end point, and why addressing sleep habits alongside it matters.
Can I take melatonin every night, or long term?
UK licensing is for short-term use. Prolonged-release melatonin is licensed for up to thirteen weeks of daily treatment, and immediate-release melatonin for jet lag is licensed for up to five days per trip. Taking it every night indefinitely goes beyond what the licence covers and should only happen under the supervision of a prescriber who has reviewed whether it is still helping and whether something else is driving your sleep problem. If you find you cannot stop, that is a signal to revisit the underlying cause rather than to continue by default.
How long does melatonin take to work?
Immediate-release melatonin is absorbed quickly and blood levels peak within about an hour, which is why jet-lag dosing is tied closely to bedtime. Prolonged-release melatonin is deliberately slower, which is why it is taken one to two hours before bed. How long before you notice a difference in your sleep is a separate question, and the Circadin leaflet does not commit to a timeline. Some people notice an effect on the first night, while for others any benefit builds over the first week or two of consistent use. Taking it at the same time each night matters more than the exact interval before bed.
Is melatonin available over the counter in the UK?
No. Every melatonin product licensed in the UK is a prescription-only medicine, so it cannot be sold over the counter in pharmacies, supermarkets or health-food shops. This differs from the United States, where melatonin is regulated as a dietary supplement and sold in shops. To obtain it legally in the UK you need a prescription from a doctor or another registered prescriber, which can be issued either at an appointment or through a regulated online pharmacy consultation.
Can I take melatonin with other medicines?
Not always, and it is worth checking before you start. Melatonin should not be combined with fluvoxamine, which can raise melatonin levels many times over. It may affect the activity of anticoagulants such as warfarin, and it adds to the sedative effect of benzodiazepines and Z-drugs. Oestrogens and cimetidine increase melatonin levels, while carbamazepine and rifampicin reduce them. Alcohol reduces melatonin's effect on sleep. Tell your prescriber about every medicine you take, including anything bought without a prescription, before starting melatonin.
References
- Electronic medicines compendium. Circadin 2 mg Prolonged-release Tablets — Summary of Product Characteristics. medicines.org.uk
- Electronic medicines compendium. Circadin 2 mg Prolonged-release Tablets — Patient Information Leaflet. medicines.org.uk
- Electronic medicines compendium. Melatonin 3 mg film-coated tablets — Summary of Product Characteristics. medicines.org.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summaries: Insomnia. cks.nice.org.uk
- Ferracioli-Oda E, Qawasmi A, Bloch MH. Meta-analysis: melatonin for the treatment of primary sleep disorders. PLoS ONE, 2013;8(5):e63773. pubmed.ncbi.nlm.nih.gov
- British National Formulary. Melatonin. bnf.nice.org.uk
- NHS. Insomnia. nhs.uk
Medical disclaimer: This article is for informational purposes only and does not replace individual medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.