Melatonin for jet lag
Melatonin is a timing signal, not a sleeping pill. The hour it is taken decides which way it moves the body clock, and the wrong hour moves the clock away from where a traveller needs it.
What melatonin does
Melatonin is the hormone the body releases as darkness falls. Its rise is the internal announcement that night has begun. Taking melatonin adds that announcement at an hour you choose, and the body clock responds by moving towards it.
That makes melatonin a timing signal rather than a sedative. It is far weaker than light as a clock mover, and it works only when the hour is right. Taken at the wrong hour it pushes the clock in the wrong direction, which lengthens jet lag rather than shortening it.
Timing decides the direction
The rule mirrors the rule for light, reversed. Melatonin taken in the early evening advances the clock, which is what an eastward traveller needs. Melatonin taken on waking delays the clock, which is what a westward traveller needs.
| Travelling east | Clock must advance |
|---|---|
| Eastward timing | About five hours before target bedtime |
| Travelling west | Clock must delay |
| Westward timing | On waking, at the start of the target day |
| Dose range in phase shifting trials | 0.5 to 5 milligrams |
| Effect of a larger dose | More sedation, not a larger phase shift |
| Relative strength | Weaker than timed bright light |
The Jet Lag Calculator places the melatonin window on each day of your plan, on the correct side for your direction of travel, and moves it as your body clock moves. You can switch the melatonin windows off if you would rather plan light and sleep alone.
Practical points
- A westward morning dose can cause drowsiness. Do not drive after taking it.
- Melatonin supports the light schedule rather than replacing it. Skipping the light windows removes most of the effect.
- Product strength varies widely, and in unregulated markets the stated dose and the actual dose do not always match.
- Alcohol works against both sleep quality and circadian timing. It undoes on a flight what melatonin is being taken to achieve.
Questions about melatonin and jet lag
Does melatonin cure jet lag?
No. Melatonin shifts the timing of the body clock and can shorten the adjustment. It does not remove the sleep debt a long flight creates, and it works only when the timing is correct. Timed bright light moves the clock further than melatonin does.
When should melatonin be taken for an eastward flight?
For eastward travel, which needs the clock to run earlier, melatonin is taken in the early evening, roughly five hours before the target bedtime. The Jet Lag Calculator marks that window on every preparation and settling day of the plan.
When should melatonin be taken for a westward flight?
For westward travel, which needs the clock to run later, melatonin is taken on waking rather than at night. Because it can cause drowsiness, a morning dose is not compatible with driving or operating machinery.
What dose is used in the research?
Trials on circadian phase shifting have generally used low doses in the range of 0.5 to 5 milligrams. Larger doses do not produce a larger phase shift. They mainly increase the sedative effect and the chance of grogginess the next day. Dose and suitability are decisions for a clinician or pharmacist.
Is melatonin available everywhere?
No. Melatonin is sold over the counter in some countries and is prescription only in others, including the United Kingdom and much of the European Union. Check the rules in both the country you live in and the country you are travelling to.
Who should avoid melatonin?
Melatonin is not suitable for everyone. Pregnancy, breastfeeding, epilepsy, autoimmune conditions and several medications including anticoagulants and immunosuppressants are all reasons to take advice before using it. Speak to a clinician or pharmacist before a first dose.