Melatonin for jet lag: timing, dose, and what the research shows

Melatonin can reduce jet lag, but timing matters far more than dose. The strongest evidence supports taking it close to your target bedtime at the destination after crossing five or more time zones, especially travelling east. Higher doses are not more effective. And in the UK, melatonin is a prescription-only medicine rather than a supplement off the shelf. This guide sets out what the research actually shows, and what that means in practice.

Does melatonin work for jet lag?

Yes, within limits. Melatonin is the hormone your body releases at night to signal darkness, and taking it as a supplement can nudge the clock and ease jet lag symptoms. The strongest evidence is a Cochrane review of ten trials: eight found that melatonin taken close to target bedtime at the destination reduced jet lag after flights crossing five or more time zones, and the reviewers judged it effective for this purpose and safe for occasional short-term use (Herxheimer & Petrie, Cochrane review). The benefit is clearest on larger time-zone shifts and when travelling east. For smaller shifts of two or three zones, the evidence is weaker and timed light is usually enough.

When to take melatonin

Timing is the part that most people get wrong, and it is what determines whether melatonin helps or does nothing. The Cochrane evidence points to taking it close to the target bedtime at your destination, in the local late evening, once you have arrived. Taken at the right time it reinforces the new biological night; taken at the wrong time it can shift the clock the wrong way.

Because the clock has to move in opposite directions depending on travel direction, the practical timing differs east versus west, which is why generic advice falls short. The asymmetry is explained in eastward versus westward jet lag. The simplest reliable approach is to take it at destination bedtime for a few nights after arrival, and to pair it with correctly timed daylight, which does most of the heavy lifting in resetting the body clock. Your GP can give you timing guidance specific to your route.

How much to take, and why more is not better

Melatonin follows a counterintuitive pattern: beyond a low threshold, more does not mean better. Trials have found low amounts to be as effective as higher ones for jet lag, while higher amounts are more likely to cause grogginess and next-day drowsiness. The Cochrane review found no advantage to larger doses. In other words, the dose-response is flat or even U-shaped above a small effective amount, so taking more is likely to leave you feeling worse, not recover faster.

For that reason this guide does not recommend a specific dose. The licensed and evidence-supported ranges are modest, and the right amount and form for you is a decision for your GP, who can also advise on timing and on any interaction with other medicines. The headline to carry into that conversation is simple: timing beats dose.

Melatonin is prescription-only in the UK

This is the practical point that catches British travellers out. In the UK, melatonin is classed by the MHRA as a prescription-only medicine: no pharmacy or health-food shop can legally sell it without a prescription. It is licensed in the UK for short-term use, and obtaining it for jet lag means asking your GP. The NHS guidance on melatonin sets out how it is used.

In the United States, by contrast, melatonin is sold over the counter as a dietary supplement with minimal oversight, which creates a separate problem worth knowing about if you buy it abroad. An analysis of over-the-counter products found the actual melatonin content fell outside 10 per cent of the labelled amount in more than seven in ten supplements, ranging from 83 per cent below to nearly five times above the stated dose, with some products also containing the contaminant serotonin (Erland & Saxena, label-accuracy analysis). A US over-the-counter bottle, in short, may not contain what the label claims.

What melatonin does not do

Melatonin is not a sleeping pill in the conventional sense. It shifts the timing of the body clock rather than sedating you, so it works by signalling night, not by knocking you out, and it will not override a clock that is pointed the wrong way if the timing is off. It also addresses only the timing layer of recovery. The fatigue of a long flight, from cabin conditions and lost sleep, is a separate matter that melatonin does not touch, as covered in jet lag versus travel fatigue. And it is one tool among several: the wider options are reviewed in our guide to evidence-based jet lag remedies.

Beyond melatonin: light and recovery

Light remains the most powerful lever for resetting the clock, and melatonin works best as a support to well-timed light rather than a substitute for it. For travellers who also want to support how the body feels and functions while the clock realigns, there is a physiological recovery layer beyond timing. Aurion Reset is a clinician-supervised recovery protocol at the Aurion clinic in Mayfair, designed for travellers landing into a demanding schedule. A session lasts 75 minutes, including a clinician consultation and 45 minutes of active PureFlow™, heart-synchronised pneumatic compression designed to support circulation and oxygenation while you remain at rest.

Frequently asked questions

When should I take melatonin for jet lag?

The evidence supports taking melatonin close to your target bedtime at the destination, in the local late evening, once you have arrived, for a few nights. Timing is more important than dose, because melatonin shifts the clock and the wrong timing can move it the wrong way. The exact timing depends on whether you flew east or west, so ask your GP for guidance specific to your route.

How much melatonin should I take for jet lag?

This is a question for your GP rather than a number to copy from an article. The evidence shows that higher amounts are not more effective and are more likely to cause next-day grogginess, so the effective amounts are modest. Because melatonin is a prescription-only medicine in the UK, the dose and form will be decided with your doctor, who can match it to your travel and any other medicines.

Can I buy melatonin over the counter in the UK?

No. In the UK melatonin is a prescription-only medicine, so it cannot legally be sold without a prescription, and you would obtain it through your GP. This differs from the United States, where it is sold as an over-the-counter supplement. Be aware that the content of US over-the-counter products often differs from the label, so a bottle bought abroad may not contain the stated amount.

Does melatonin work for westward travel?

It can, but the benefit is clearest travelling east and across larger time-zone shifts. Travelling west, the clock has to delay rather than advance, and well-timed evening light often does most of the work, so melatonin plays a smaller role. The Cochrane evidence is strongest for eastward flights crossing five or more time zones.

Is melatonin safe to use for jet lag?

For occasional short-term use, melatonin is generally considered safe, and the Cochrane review found no serious problems in the trials it assessed. Because it is a prescription-only medicine in the UK, use it under your GP’s guidance, who can check for interactions with other medicines and advise on timing. It is not intended as a long-term sleep aid for frequent use without medical advice.