Melatonin is the hormone your brain releases when it gets dark — the body's internal "night is here" signal. Taken deliberately when travelling, it can nudge your body clock toward local time faster than it would drift on its own, which is why it's the best-evidenced medical option for jet lag. The catch: when you take it matters far more than how much, because you're using it to move a clock, not to knock yourself out.
Melatonin is a signal, not a sedative
This is the most important thing to understand, because it changes how you use it. Sleeping tablets work by sedation — they force sleep chemically. Melatonin works by information: it tells your master body clock "it's night-time now", and the clock adjusts its whole schedule in response. Some people do feel drowsy after taking it, but that drowsiness is a side effect, not the mechanism. The real action is shifting the timing of your circadian rhythm — which is exactly what jet lag needs, since jet lag is a timing problem.
How your body normally uses it
In an unshifted body, melatonin rises a couple of hours before your usual bedtime, peaks overnight, and falls before morning — bright light strongly suppresses it (which is why late-night screens hurt sleep). When you fly across time zones, your melatonin is still rising and falling on home schedule, out of step with local darkness. Taking melatonin at a strategically chosen local time helps drag that internal rhythm around to match where you actually are.
What the evidence says
Jet lag is one of melatonin's best-supported uses. Reviews of multiple trials have found melatonin, taken close to the target bedtime at the destination, is effective at reducing jet lag after crossing several time zones — with benefit generally clearest on longer trips (five or more zones) and eastward journeys, the hardest direction. It's considered a low-risk option for short-term travel use in appropriate people, which is a large part of why clinicians reach for it over sleeping tablets for jet lag.
Why timing beats dose
Because melatonin shifts the clock, taking it at the wrong time can shift your clock the wrong way and make jet lag worse — the one genuine pitfall. The right timing depends on which direction you flew and how many zones you crossed, so it's not a "take one at bedtime and hope" medicine. We've dedicated a full guide to getting this right: when to take melatonin for your direction of travel. On dose, more is not better — higher doses mainly increase grogginess without shifting the clock faster, and lower physiological-range doses are often used precisely because timing does the real work.
Melatonin is prescription-only in the UK
Unlike in the US, where it's sold as a supplement, melatonin is a prescription medicine in the UK — which means quality-controlled dosing and a clinician checking it's right for you, rather than a guess off a shop shelf. It means one practical thing for travellers: sort it before you fly, not at your destination. A short travel consultation can assess whether it's suitable, since it isn't right for everyone — see is melatonin safe? what to know before you fly.
It works best as part of a package
Melatonin isn't magic on its own — it performs best combined with the free tools that shift the same clock: strategic light exposure (the single most powerful lever), adjusting meal times toward local schedule, and good sleep habits at the destination. Think of melatonin as one instrument in the section, with light as the lead — our guide to beating jet lag with light, food and sleep covers the rest.
Frequently asked questions
Does melatonin actually work for jet lag?
Yes — it's the best-evidenced option, most effective for trips of five or more time zones and eastward travel, when taken close to destination bedtime. Correct timing is essential to the benefit.
Is melatonin a sleeping pill?
No — it signals your body clock that it's night rather than sedating you. Some drowsiness can occur, but the main effect is shifting your circadian rhythm's timing.
Can I buy melatonin over the counter in the UK?
No — it's a prescription-only medicine here, unlike in the US. Arrange it before travelling via a clinician who can check it suits you.
Does a higher dose work better?
Generally no — higher doses tend to increase grogginess without shifting the clock faster. Timing relative to your travel direction matters far more than dose size.
References
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. 2002;(2):CD001520.
- Arendt J. Managing jet lag: some of the problems and possible new solutions. Sleep Med Rev. 2009;13(4):249–256.
- British National Formulary. Melatonin. bnf.nice.org.uk.
- NHS. Jet lag. nhs.uk/conditions/jet-lag.