Melatonin is the most widely purchased sleep supplement globally — yet in the UK, it has a unique and somewhat confusing regulatory status. Understanding what melatonin actually does, what the evidence shows, and the legal routes to accessing it helps you make an informed decision.
What Melatonin Does
Melatonin is a hormone produced by the pineal gland in the brain in response to darkness — it is the body’s “darkness signal” to the circadian clock. It doesn’t cause sleep directly but signals that it’s night-time, shifting the circadian phase and promoting sleep onset. This makes it most effective for circadian rhythm-related sleep problems — jet lag, delayed sleep phase, shift work — rather than for primary insomnia where the circadian system is already appropriately timed.
What the Evidence Shows
Jet lag: the strongest evidence for melatonin. Multiple RCTs confirm that melatonin (0.5–5mg taken at bedtime at the destination) reduces jet lag symptoms — daytime fatigue, impaired concentration, disturbed sleep — when crossing multiple time zones, particularly eastward travel. Delayed sleep phase disorder (DSPD): people who can’t fall asleep until very late (e.g. 2–4am) and struggle to wake at normal times can use low-dose melatonin (0.5mg, 5–6 hours before desired sleep time) to advance their circadian phase. This works through chronobiotic effects rather than sedation. Sleep in older adults: natural melatonin production declines significantly after age 55. Circadin (2mg prolonged-release melatonin) is the only prescription melatonin licensed in the UK — specifically for short-term insomnia in adults over 55. Multiple trials confirm improved sleep quality and morning alertness with minimal side effects or next-day grogginess (unlike benzodiazepines). Primary insomnia in general adults: evidence is less robust. Low-dose melatonin (0.5–1mg) may modestly improve sleep onset. It doesn’t address the hyperarousal that drives most insomnia and is generally less effective than CBT-I.
Regulatory Status in the UK
In the UK, melatonin is a prescription-only medicine (POM) for adults — the licensed product Circadin requires a GP prescription. However, low-dose melatonin (typically 1mg or below) is available as a food supplement in health stores and pharmacies. Many people also purchase it from EU or US online retailers. The difference: licensed prescription Circadin has proven quality, bioavailability and safety data; supplement melatonin quality varies significantly. If you believe you would benefit from melatonin, discussing with your GP is the appropriate route — particularly for those over 55.
Frequently Asked Questions About Melatonin
What dose of melatonin should I take?
Less is often more with melatonin. Standard pharmacological doses in the US (3–10mg) are significantly above the physiological signalling dose — lower doses (0.5–1mg) are often equally or more effective for circadian shifting, with fewer side effects (morning grogginess at high doses). For jet lag, timing matters more than dose — taken at target bedtime, not at your departure time zone bedtime.
Is melatonin safe for children?
Melatonin (prescription, specialist-supervised) is used in children with sleep difficulties related to neurodevelopmental conditions (autism, ADHD). Paediatric melatonin use should be under GP or paediatric neurologist supervision. It is not appropriate for routine childhood sleep problems, which are better addressed through behavioural and sleep hygiene approaches.
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