Short answer: melatonin can reduce jet lag, especially after flying east across five or more time zones. What matters most is timing: it's taken around your target bedtime at your destination for a few nights after you arrive. In the UK, melatonin is a prescription medicine, so the dose comes from your prescriber, not trial and error.
What melatonin is and how it works
Melatonin is a hormone made by the pineal gland in your brain. Levels rise in the evening as it gets dark and fall in the morning, which helps set your body clock (circadian rhythm) to a roughly 24-hour cycle.
Taking melatonin at the right time tells your brain it's night-time in your new location, even when your body still thinks you're at home. That helps your body clock catch up with local time faster than it would on its own.
Why jet lag happens
Jet lag happens because your body clock stays on home time after you've crossed time zones. Land in Singapore at 10am after an overnight flight from London and your body thinks it's about 2am. The more time zones you cross, the bigger the mismatch, and the longer it takes to adjust. Symptoms include poor sleep at night, sleepiness during the day, poor concentration and an upset stomach.
Does melatonin work for jet lag?
A Cochrane review of the trials found that melatonin taken close to the target bedtime at the destination reduced jet lag after flights crossing five or more time zones. The benefit was most consistent after flying east.
East versus west
Flying east means going to bed earlier than your body wants, which is harder to adjust to, and this is where melatonin helps most. Flying west means staying up later, which most people find easier. Melatonin may still help you sleep through the night after a westward flight.
How many time zones?
If you cross only one or two time zones, your body will usually adjust within a day or two without any medicine. Melatonin is most useful for longer trips, such as Europe to Asia, Australia or the west coast of America.
Dosage: why your prescriber decides
In the UK, melatonin is a prescription-only medicine. It isn't sold as a supplement here. Your prescriber will recommend a dose based on the product you're given and your health, and the instructions will be on the label and in the patient leaflet. Take it as prescribed and don't increase the dose yourself. More isn't necessarily better: higher doses are more likely to leave you groggy the next day.
When to take it
Timing makes more difference than dose.
- Take it at your usual bedtime in local time at your destination, not when you'd go to bed at home.
- Don't take it before 8pm or after 4am local time. Taken at the wrong time, it can push your body clock the wrong way.
- Start on the day you arrive and continue for a few nights, up to 5 nights in a row, until you're falling asleep easily at the local bedtime.
- Go to bed soon after taking it, and don't drink alcohol with it.
As a rough guide, London to New York (five hours behind) may need two or three nights, while London to Sydney may need the full course.
Side effects and safety
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Melatonin is usually well tolerated. Side effects can include headache, feeling sleepy or dizzy during the day, irritability, tummy pain or feeling sick, and vivid dreams.
- Driving: melatonin can make you drowsy. Don't drive or use machinery for at least 8 hours after a dose if you feel sleepy. Bear this in mind if you're picking up a hire car.
- Alcohol: avoid it. Alcohol can make melatonin less effective and disturbs sleep anyway.
- Pregnancy and breastfeeding: melatonin isn't recommended.
- Children: not for under-18s unless a specialist advises it.
- Other medicines: don't take melatonin with fluvoxamine (an antidepressant), as it raises melatonin levels a lot. Tell the prescriber if you take some antibiotics (quinolones such as ciprofloxacin), cimetidine, the contraceptive pill or HRT, carbamazepine, rifampicin, sleeping tablets or other sedating medicines, or warfarin.
Other ways to beat jet lag
Melatonin works best alongside simple changes, and for short trips these may be all you need:
- Shift your sleep before you go. For a few days before an eastward flight, go to bed and get up an hour earlier each day; before a westward flight, an hour later.
- Use daylight. After flying east, get outside in the morning light. After flying west, get light in the afternoon and early evening.
- Switch to local time straight away. Eat meals and go to bed at local times. If it's night-time at your destination, try to sleep on the plane.
- Avoid long naps on arrival. If you must nap, keep it to 20 to 30 minutes.
- Drink water on the flight and go easy on alcohol and caffeine.
For more ways to adjust, see our jet lag treatment page, which explains how to request melatonin through an online consultation. If you're travelling further afield, see our travel health checklist and our pages on malaria prevention, altitude sickness and travel sickness.
Melatonin for jet lag FAQs
How long before bed should I take melatonin for jet lag?
Take it at your usual bedtime in local time at your destination, then go to bed soon after. Don't take it before 8pm or after 4am local time. Follow the timing on your label if your prescriber has given different instructions.
Does melatonin work for flying west?
It may help, but the evidence is strongest for flying east, when you have to fall asleep earlier than your body wants. After a westward flight, staying up until local bedtime and getting daylight in the afternoon often does most of the work.
Can I take melatonin on the plane?
Usually not. It's started at bedtime on the day you arrive, in local time. Taking it at the wrong time can shift your body clock the wrong way and leave you drowsy when you land. Ask your prescriber if you have an unusual flight schedule.
Is melatonin available without a prescription in the UK?
No. In the UK melatonin is a prescription-only medicine. You need a prescription from a doctor or other prescriber, including through an online consultation with a UK pharmacy.
Can I drink alcohol with melatonin?
It's best not to. Alcohol can make melatonin less effective, adds to drowsiness and makes sleep worse, which is the opposite of what you want when you're trying to adjust.
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