Circadin (Prolonged-Release Melatonin 2mg): Uses, Dose and Side Effects
What Circadin is licensed for, how to take it properly, and how it differs from ordinary melatonin.
Part of our Sleep condition guide.
In short: Circadin is a 2mg prolonged-release melatonin tablet that releases slowly overnight to mimic the body's natural melatonin profile. It is licensed in the UK for the short-term treatment of primary insomnia characterised by poor quality of sleep, in adults aged 55 and over, and is taken one to two hours before bed after food.
Circadin From a UK Registered Pharmacy
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View Circadin →What Circadin is
Circadin is a brand of melatonin. Specifically, it is a 2mg prolonged-release tablet — the original licensed prolonged-release melatonin product in the UK and Europe, and the one most other prolonged-release melatonin tablets are equivalents of.
Melatonin itself is a hormone your pineal gland produces. Levels rise a couple of hours before your usual bedtime, peak overnight, and fall towards morning. That rhythm is the body's internal signal that it is night, and it is the signal Circadin is designed to reinforce.
Circadin is not a sleeping tablet in the conventional sense. It does not sedate you the way zopiclone or a sedating antihistamine does. Its patient information makes the point directly: it works by supplementing a hormone rather than by switching off the parts of the brain that keep you awake. That difference is worth holding onto, because it shapes what to expect.
How prolonged release changes what it does
Ordinary immediate-release melatonin dissolves quickly. Blood levels spike within about an hour and then fall away. That sharp evening peak is very good at doing one particular thing: shifting the body clock, which is why immediate-release melatonin is the formulation licensed for jet lag.
A prolonged-release tablet does the opposite. The melatonin is released gradually across the night, producing a lower, longer curve that resembles the body's own overnight profile far more closely than a spike does.
Immediate-release: a spike
Sharp peak within about an hour, then gone. Effective at moving the clock. Not present at 4am when many people wake.
Circadin: a curve
Slow release across the whole night. Supports the natural overnight signal rather than shifting it. Better suited to staying asleep.
This is why the two products are not interchangeable, and why swapping one for the other because it is cheaper or easier to get is a mistake. They solve different problems.
Who Circadin is licensed for
The licensed indication is precise, and it is worth quoting rather than paraphrasing: Circadin is indicated as monotherapy for the short-term treatment of primary insomnia characterised by poor quality of sleep in patients who are aged 55 or over.
Three parts of that sentence do real work.
| Phrase | What it means in practice |
|---|---|
| Short-term | Up to thirteen weeks of treatment, not an indefinite nightly tablet |
| Primary insomnia | Insomnia in its own right — not sleep disturbed by pain, depression, sleep apnoea, restless legs, reflux or a medication side effect. Those need the underlying cause treated |
| Poor quality of sleep | The trials looked at how restorative sleep felt and how alert people were the next morning, not simply how many hours they logged |
| Aged 55 or over | Natural melatonin production declines with age, so an older adult with insomnia is more likely to have a genuine shortfall in the signal |
2mg
the licensed dose — one tablet daily
55+
the licensed age group
13 weeks
the maximum licensed treatment period
If you are under 55, Circadin is outside its licence for you. A prescriber may still consider it in some circumstances, but that is an off-licence decision they should discuss with you explicitly, and it is not something to assume.
How to take Circadin
1
One 2mg tablet, once daily
The dose is one tablet. There is no titrating up: 2mg is the licensed dose for adults, and taking two tablets does not make it work better.
2
One to two hours before bedtime
Not as you get into bed. The prolonged-release mechanism needs a head start, so take it while you are still winding down rather than at lights-out.
3
After food
The licensed instruction is to take it after food. Building it into a fixed evening routine also makes it far easier to take at a consistent time, which matters for a medicine that works as a timing signal.
4
Swallow whole — never crush, break or chew
The slow release depends entirely on the tablet staying intact. Crushing or halving it dumps the whole 2mg at once, which converts a night-long release into an immediate one and defeats the purpose of the product.
The swallow-whole instruction is not a formality. If you have difficulty swallowing tablets, tell your prescriber before starting rather than breaking the tablet — a different formulation may be more appropriate for you.
How long you can take it
Circadin is licensed for up to thirteen weeks. That is a genuine limit, not a cautious default, and it reflects both the duration of the trials behind the licence and the intention that melatonin treats a short-term problem rather than becoming permanent furniture.
In practice this means treatment should have a review point. If sleep has improved, the sensible next step is to stop and see whether the improvement holds, ideally with better sleep habits established underneath it. If sleep has not improved, continuing for another three months is unlikely to change that, and the better question is what else is going on.
Stopping is straightforward. The patient information leaflet states that there are no known harmful effects if treatment is interrupted or ended early, and that Circadin is not known to cause withdrawal effects after treatment completion. You do not need to taper it.
Circadin side effects
Circadin is generally well tolerated. Notably, the side effects listed in its product information are classed as uncommon — meaning they affect between 1 in 1,000 and 1 in 100 people — rather than common.
| Frequency | Reported effects |
|---|---|
| Uncommon 1 in 1,000 to 1 in 100 | Headache, migraine, lethargy, dizziness, somnolence (sleepiness); irritability, nervousness, restlessness, anxiety; abnormal dreams and nightmares; insomnia |
| Rare 1 in 10,000 to 1 in 1,000 | A wider range of effects reported infrequently, including mood changes, visual disturbance and abdominal symptoms — see the patient information leaflet supplied with your medicine for the full list |
Two entries on that list surprise people. Vivid dreams and nightmares are a recognised effect of melatonin — unsettling, but not dangerous. And insomnia appearing on a list of side effects for an insomnia treatment is not a misprint; a minority of people find melatonin has the opposite effect to the one intended, which is a reason to stop and reconsider rather than to increase the dose.
Driving. Circadin may cause drowsiness and has a moderate influence on the ability to drive and use machines. Do not drive or operate machinery if you are affected, and speak to your prescriber if drowsiness continues into the day.
Who should not take it, and interactions
Circadin is contraindicated if you are hypersensitive to melatonin or to any of the tablet's other ingredients. Beyond that, it is not recommended in several situations:
- Autoimmune conditions — melatonin has immune-modulating effects and is not recommended in autoimmune disease
- Hepatic impairment — melatonin is cleared by the liver, and use is not recommended in people with liver impairment
- Pregnancy and breastfeeding — not recommended; there is a lack of clinical data, and melatonin passes into breast milk
- Under 18s — safety and efficacy have not been established in patients aged 0 to 18 years
- Galactose intolerance and related rare hereditary conditions — the tablets contain lactose
Interactions matter here more than people expect, because melatonin is metabolised largely by the liver enzyme CYP1A2, and quite a few common medicines affect it.
| Medicine | Effect |
|---|---|
| Fluvoxamine | Raises melatonin levels dramatically — around 17 times the exposure. This combination should be avoided |
| Cimetidine | Increases plasma melatonin levels |
| Oestrogens (including some contraceptives and HRT) | Increase melatonin levels by inhibiting its metabolism |
| Carbamazepine, rifampicin | Reduce plasma melatonin concentrations, potentially making it less effective |
| Benzodiazepines and Z-drugs | Sedative effects add together |
| Warfarin and other anticoagulants | Melatonin may affect anticoagulant activity — discuss with your prescriber |
| Smoking | Induces CYP1A2 and can reduce melatonin levels, so smokers may get less effect from the same dose |
Circadin and alcohol
They work against each other. The product information is explicit that alcohol reduces the effectiveness of Circadin on sleep, and alcohol independently fragments the second half of the night — which is precisely the part of the night a prolonged-release tablet is meant to support.
An occasional glass of wine is not a crisis, but if you are drinking most evenings and taking Circadin, you are unlikely to get a fair test of whether the medicine works. It is worth a fortnight without alcohol before concluding Circadin has failed.
If Circadin does not seem to be working
Before assuming the medicine is the problem, work through this list — most cases have a fixable explanation.
- Are you taking it one to two hours before bed? Taking it at lights-out is the single most common reason it underperforms
- Are you swallowing it whole? A broken or crushed tablet is no longer a prolonged-release product
- Are you taking it at a consistent time? A timing signal delivered at a different time each night is a weak signal
- Are you drinking alcohol in the evening? It directly reduces the effect
- Have you given it long enough? Expectations calibrated to a sedative will be disappointed by a hormone; the effect is gentler than a sleeping tablet's
- Is something else disturbing your sleep? Pain, reflux, needing the toilet, restless legs, snoring with daytime sleepiness, low mood or anxiety — none of these respond to melatonin, and all of them are treatable in their own right
That last point is the important one. Circadin is licensed for primary insomnia. If your sleep is being broken by something else, the useful step is identifying it, not adjusting the melatonin.
Circadin or the generic version?
Circadin was the original brand, and its patent has since expired, so generic prolonged-release melatonin 2mg tablets are now available. They contain the same active ingredient at the same strength in the same prolonged-release form, and they are licensed on the basis of being equivalent to the brand.
The practical difference is price. If cost is a factor over a course lasting up to thirteen weeks, the generic is worth asking about — it is the same medicine.
Original brand
Circadin 2mg Prolonged-Release
The originator prolonged-release melatonin tablet, 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 in a generic prolonged-release tablet.
View treatment →What is not an equivalent swap is immediate-release melatonin 3mg. It is a different release profile licensed for a different condition, and it will not do what Circadin does. Our side-by-side comparison of melatonin vs Circadin sets out why.
How to get Circadin in the UK
Circadin is a prescription-only medicine, so it cannot be bought over the counter — a point that catches out anyone who has seen melatonin on sale abroad. Our guide to buying melatonin over the counter in the UK explains the law and why imported products carry a quality risk.
You can get it from your NHS GP where clinically appropriate, or through a regulated online pharmacy such as our sleep treatment service, where you complete a clinical questionnaire and a registered prescriber decides whether Circadin is suitable for you. Both routes involve an assessment — including a check of your other medicines, given the interaction list above.
Request Circadin From a UK Pharmacy
Complete a short online consultation and a GPhC-registered pharmacist independent prescriber will review your sleep problem, your medical history and your other medicines. Dispensed from our UK pharmacy, registration 9011198, with no GP appointment needed.
Start a Consultation →Frequently Asked Questions
What is Circadin used for?
Circadin is licensed in the UK as monotherapy for the short-term treatment of primary insomnia characterised by poor quality of sleep, in adults aged 55 and over. It is a 2mg prolonged-release melatonin tablet that releases melatonin slowly across the night, supporting the body's own overnight melatonin signal rather than sedating you. It is intended for insomnia in its own right, not for sleep disturbed by another cause such as pain, reflux, sleep apnoea or low mood, which need treating directly.
How long does Circadin take to work?
The patient information leaflet does not give a timeline, and in practice it varies. Some people notice a difference within the first few nights, while for others any benefit builds over the first week or two of consistent use. Because Circadin supplements a hormone rather than sedating you, the effect is gentler than a conventional sleeping tablet, and people expecting to feel switched off sometimes conclude it has not worked when it has. Taking it at the same time each evening, one to two hours before bed, gives it the best chance.
How long can you take Circadin for?
Circadin is licensed for up to thirteen weeks of treatment. It is intended as a short-term measure with a review point rather than an indefinite nightly tablet. Stopping is straightforward: the patient information leaflet states there are no known harmful effects if treatment is interrupted or ended early, and that Circadin is not known to cause withdrawal effects after treatment completion, so no tapering is needed. If your sleep has not improved after a full course, continuing is unlikely to help and it is worth reviewing what else may be driving the problem.
What is the difference between Circadin and normal melatonin?
The difference is how the melatonin is released. Circadin is a prolonged-release tablet: the 2mg dose is released gradually across the night, producing a low, long curve resembling the body's natural overnight profile, which suits difficulty staying asleep. Ordinary immediate-release melatonin, such as the 3mg tablets licensed for jet lag, dissolves quickly and produces a sharp peak within about an hour, which is effective at shifting the body clock but has largely worn off by the early hours. They are licensed for different conditions and are not interchangeable.
Is there a cheaper generic version of Circadin?
Yes. Circadin was the original brand and generic prolonged-release melatonin 2mg tablets are now available, containing the same active ingredient at the same strength in the same prolonged-release form. They are licensed on the basis of being equivalent to the brand, so the meaningful difference is price rather than the medicine. Over a course lasting up to thirteen weeks that can add up, so it is worth asking your prescriber about the generic. Immediate-release melatonin 3mg is not a cheaper alternative to Circadin, because it is a different product for a different purpose.
Can you take Circadin if you are under 55?
Circadin's UK licence covers adults aged 55 and over, so prescribing it to someone younger is outside the licensed indication. A prescriber may still consider it in particular circumstances, but that is an off-licence decision they should discuss with you explicitly, including the reasoning and what to expect. Safety and efficacy have not been established in anyone aged under 18, and the adult products should not be used in children or adolescents. If you are under 55 with persistent insomnia, cognitive behavioural therapy for insomnia is the treatment with the strongest evidence.
Do you need a prescription for Circadin in the UK?
Yes. Circadin, like every other melatonin product in the UK, is a prescription-only medicine and cannot be bought over the counter in a pharmacy, supermarket or health-food shop. You can obtain it through your NHS GP where clinically appropriate, or through a regulated online pharmacy where you complete a clinical questionnaire and a registered prescriber decides whether it is suitable for you. That assessment includes checking your other medicines, which matters because several common drugs interact with melatonin.
Can you drink alcohol while taking Circadin?
It is better not to. The product information states that alcohol reduces the effectiveness of Circadin on sleep, so drinking in the evening works directly against the medicine. Alcohol also fragments sleep in the second half of the night, which is precisely the period a prolonged-release tablet is intended to support. An occasional drink is unlikely to be harmful, but if you drink most evenings you will not get a fair impression of whether Circadin is helping. Trying a couple of weeks without alcohol is a reasonable test.
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
- British National Formulary. Melatonin. bnf.nice.org.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summaries: Insomnia. cks.nice.org.uk
- European Medicines Agency. Circadin: EPAR product information. ema.europa.eu
Medical disclaimer: This article is for informational purposes only and does not replace individual medical advice. Always read the patient information leaflet supplied with your medicine and consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.