Read this first
This is general information, not medical advice. Supplements can interact with medicines and aren’t suitable for everyone, especially in pregnancy or with a medical condition. Talk to a pharmacist or doctor before starting one.
What it is
Melatonin is a hormone made by the pineal gland in the brain, rising in the evening to signal night-time. Supplements copy that signal. It is not a peptide, and the oral form is a different product from the injectable melatonin covered on the peptides section of this site.
In the UK, melatonin is a prescription-only medicine (for example Circadin for insomnia in people aged 55 and over, and other forms prescribed by specialists). In the US and many other countries it is sold over the counter as a supplement, which is why people often buy it online or bring it back from abroad.
How it works
Melatonin acts on receptors in the brain's body clock and tells your body it is night. It is better at shifting when you feel sleepy than at forcing sleep, so it tends to help more with jet lag, shift work and delayed sleep timing than with general insomnia.
What the evidence says
- Moderate Jet lag
Reviews suggest it can reduce jet lag symptoms, especially after crossing several time zones eastward. - Moderate Falling asleep faster
On average it shortens the time to fall asleep by a small amount, often about 7 to 10 minutes in reviews. - Moderate Shift work and delayed sleep phase
Timing matters a lot; taken at the wrong time it can make things worse. - Limited General insomnia
Effects are modest and less than many people expect. - Moderate Sleep in children with certain conditions
Used under specialist supervision for conditions such as ADHD or autism-related sleep problems.
Evidence ratings are our plain-English summary of how much good human research exists, not a promise of results. How we rate evidence.
Dosage and timing
- Lower doses of 0.5 to 3 mg are generally as effective as higher ones for most people; more is not better.
- For sleep onset, take 1 to 2 hours before bed. For shifting your body clock, timing matters more than dose and is worth reading up on.
- Take consistently at the same time rather than occasionally.
- In the UK you need a prescription. Buying unlicensed products online means the dose and quality are not guaranteed.
Forms and what to look for
- Immediate-release tablets are for falling asleep; prolonged-release forms aim to cover the night.
- Gummies and sprays are convenient but the label dose is often inaccurate.
- Choose the lowest dose available.
- Avoid combination products with several other sleep ingredients you do not need.
What to expect, and when
- You may feel drowsy within an hour.
- For jet lag or body-clock shifts, benefit builds over several days.
- If nothing happens after a couple of weeks, it probably is not the right tool.
Side effects
- Headache, dizziness, nausea.
- Daytime sleepiness or grogginess, especially with high doses.
- Vivid dreams or nightmares.
- Low mood or irritability in some people.
Interactions
- Sedatives, sleeping tablets and alcohol can add to drowsiness.
- Warfarin and other blood thinners; reports of changed clotting.
- Fluvoxamine strongly raises melatonin levels.
- Blood pressure and diabetes medicines may be affected.
- Immunosuppressants and some epilepsy medicines; ask a pharmacist.
Who should avoid it
- Pregnancy and breastfeeding unless advised by a clinician.
- People with epilepsy, autoimmune conditions or on immunosuppressants should speak to their doctor.
- Driving or operating machinery after taking it.
- Children and teenagers except under medical supervision.
Risks and safety
- Prescription-only in the UK; importing or buying unlicensed products carries legal and quality risk.
- US analyses have found products containing far more or less than the label states, sometimes with serotonin.
- Long-term effects of nightly use are not well studied.
- Not on the WADA prohibited list to our knowledge.
Buying well: quality and testing
- Look for USP verification or similar third-party testing.
- Be wary of high-dose gummies, which often differ from the label.
- In the UK, use a licensed product via a prescriber or pharmacist.
- Choose single-ingredient products.
Bottom line
Oral melatonin is a useful clock-shifting tool and a mild sleep aid for some, not a sleeping pill. Low doses at the right time work best. It suits people with jet lag, shift work or delayed sleep timing, ideally via a prescription in the UK. Injectable melatonin is a different matter, covered on the melatonin peptides page.