If melatonin is not helping you sleep, you are not unusual. Melatonin is mainly a timing signal for your body clock, not a sedative. It tends to help most when the problem is a clock running late, as with jet lag. It is much weaker for ordinary long-term insomnia.
The common reasons it fails are simple. It may be taken at the wrong time or in a higher dose than helps. Your sleep problem may not be about timing at all. Caffeine or alcohol may be working against it. Or, if you buy it as a supplement, the product may not contain what the label says.
For long-term insomnia, the guidelines put a talking therapy first: cognitive behavioural therapy for insomnia (CBT-I). That includes NICE, the American Academy of Sleep Medicine (AASM) and the European Sleep Research Society (ESRS).
A note on our interest
Proco sells two products that contain melatonin: Sleep Formula (2 mg) and Sleep Support (10 mg). This article does not recommend either of them. If you use both, do not take them on the same night: together they contain 12 mg of melatonin.
In Ireland and the UK, melatonin is a prescription-only medicine. If you live there, talk to your GP or pharmacist.
Melatonin is a hormone your body already makes. The NHS says it is produced just after it gets dark, peaks in the early hours and falls during daylight. The US National Center for Complementary and Integrative Health (NCCIH) says it helps with the timing of your 24-hour body clock. Light at night can block its production.
A 2026 review in the journal Clocks & Sleep put it plainly. Melatonin "acts primarily as a chronobiotic", meaning a body-clock signal, and its effects depend more on timing than dose. The authors say it is often used as if it were a "natural" sleeping pill.
That explains a lot of disappointment. People take melatonin expecting to feel knocked out, as they might with a sedative. That is not what it is for. The NHS also says it takes around 1 to 2 hours to work.
When you take melatonin matters. A 2024 meta-analysis in the Journal of Pineal Research pooled 26 double-blind randomised trials in people with insomnia and healthy volunteers. The time between taking melatonin and going to sleep was a significant predictor of how quickly people fell asleep.
The authors suggest that taking it about 3 hours before the desired bedtime may work better than the common practice of 30 minutes before. We go through this study, and how it fits with the jet lag evidence, in melatonin: the real dose-response evidence.
This is research, not a dosing instruction. Prescribed melatonin comes with its own directions. For example, the NHS says the usual prescribed slow-release tablet for short-term insomnia is taken 1 to 2 hours before bedtime. Follow your prescriber or the leaflet.
Bright light in the evening can also work against you, because light at night blocks your own melatonin.
It is tempting to take more when a low dose does not work. The evidence does not support that.
So a bigger dose may bring more side effects without more benefit. That applies to our own Sleep Support, which contains 10 mg, above that peak.
Insomnia has many causes, and most are not about the body clock. The guidelines reflect this:
Melatonin is unlikely to address problems like these:
Where melatonin does have evidence is in body-clock problems. The NCCIH lists jet lag and delayed sleep–wake phase disorder, where your natural sleep time runs very late. Even there, the AASM's recommendation for delayed sleep phase is a weak one.
The NHS lists several things that stop melatonin working well:
This applies mainly in the US, where melatonin is sold as a dietary supplement. The NCCIH says supplements are regulated less strictly than medicines.
A 2017 study in the Journal of Clinical Sleep Medicine tested 31 melatonin supplements. Melatonin content ranged from 83% below to 478% above the label. More than 71% were not within 10% of the label claim. Eight contained serotonin, which was not on the label.
That study is a few years old, and it does not tell you about any particular brand, including ours. It does mean an unexpected result may partly reflect the product. In Ireland and the UK, prescribed melatonin is a licensed medicine. The NHS advises against ordering melatonin online.
Some people find melatonin helped at first, then seemed to fade. The trial evidence on tolerance is limited but fairly consistent:
Both used a prescription prolonged-release form, and almost no trials run beyond a year. If your sleep gets worse after stopping, the original problem coming back is one possible explanation. We look at dependence, tolerance and your own melatonin production in is melatonin habit-forming?
The NHS says to ask a doctor or pharmacist about stopping if you have taken melatonin for a long time.
For long-term insomnia, the strongest evidence is for CBT-I, a structured talking therapy:
In Ireland, the HSE says most people who try CBT-I have better sleep. It can be done as guided self-help, one-to-one or in a group. Your GP may refer you to a free guided online CBT service run by the HSE with SilverCloud. In the UK, the NHS says CBT may be face to face or through an online self-help programme.
What CBT-I involves, and what its trials do and don't show, is in CBT-I: the sleep treatment with better evidence than any supplement.
While you wait, the NHS advises going to bed only when sleepy and getting up at the same time every day. Do not sleep in after a bad night.
The NHS and HSE both say GPs now rarely prescribe sleeping pills for insomnia. When they do, it is usually for a few days or weeks. The options and their limits are covered in prescription sleep medications explained.
The NHS advises seeing a GP if:
The HSE suggests talking to a GP if a sleep problem has lasted a month and new habits have not helped. Also see a GP if you snore loudly or stop breathing in your sleep, or if poor sleep comes with low mood.
Check with a doctor before using melatonin if you have epilepsy or take blood thinners (NCCIH). The NHS also lists liver or kidney problems and autoimmune conditions such as rheumatoid arthritis, multiple sclerosis or lupus. Do not drive if you feel sleepy.
If you are having thoughts of suicide: in Ireland, freephone Samaritans on 116 123 or text 50808. In the UK, call Samaritans on 116 123. In the US, call or text 988. If you are at immediate risk, call 112 or 999 (Ireland), 999 (UK) or 911 (US).
Not without advice. In pooled trials, the effect peaked at about 4 mg a day. Higher doses added mild side effects such as headache and drowsiness. Talk to your GP or pharmacist first.
It works best when the main problem is timing, such as jet lag or a body clock that runs late. It does far less for insomnia driven by stress, waking in the night or another sleep disorder.
The NHS advises not taking herbal remedies that affect sleep at the same time as melatonin, as you may become very drowsy. Both Proco products that contain melatonin also contain herbal ingredients. Ask a pharmacist before combining anything.
Only on prescription. In Ireland it is a prescription medicine and is not permitted in food supplements. In the UK, melatonin supplements are not authorised for sale. Your GP can advise whether it suits you.
This article is general information, not medical advice. Talk to your GP, pharmacist or prescriber about your own sleep problem, and before starting, stopping or changing any medicine.
Reviewed by: Proco Team
Last updated: November 2026