In short: Jet lag happens when your body clock is out of step with the local time after flying across several time zones. It causes poor sleep, daytime tiredness, low concentration and sometimes stomach upset, and usually settles within a few days. The most effective ways to reduce it are adjusting your sleep schedule, getting daylight at the right times and staying hydrated. Melatonin is a prescription-only medicine in the UK and may help some adults, but only after a prescriber has checked it is suitable.

This guide, written by a Ready Health prescribing pharmacist, explains what causes jet lag and practical, evidence-informed ways to reduce it.

What is jet lag?

Your body runs on an internal clock, known as the circadian rhythm, that controls when you feel sleepy or alert, as well as hunger, digestion and body temperature. When you cross time zones quickly, this clock stays on home time for a while. The mismatch between your body clock and local time is jet lag. It is usually worse after crossing more time zones, and many people find flying east (for example, from Manchester to Asia) harder than flying west, because it means going to sleep earlier than your body expects.

What are the symptoms of jet lag?

Difficulty falling asleep at night or waking very early
Daytime sleepiness and tiredness
Poor concentration and memory
Irritability or low mood
Loss of appetite, indigestion, constipation or diarrhoea
Feeling generally unwell or light-headed

Symptoms usually improve within a few days, though it can take longer after long-haul eastward trips.

How can I prevent jet lag before I fly?

Shift your sleep gradually: for a few days before travel, go to bed and get up an hour earlier (if flying east) or later (if flying west).
Start the trip well rested: sleep loss before travelling makes jet lag worse.
Plan for important events: on short trips of a day or two, it may be better to stay on home time where possible.

What can I do during the flight?

Set your watch or phone to destination time when you board.
Drink plenty of water and limit alcohol and caffeine, which can disturb sleep and add to dehydration.
Sleep on the plane if it is night-time at your destination; use an eye mask and earplugs.
Move around and stretch regularly on long flights to reduce the risk of blood clots.

How do I get over jet lag after arriving?

Use daylight: light is the strongest signal for resetting your body clock. Spend time outdoors in daylight, particularly in the morning after flying east and in the late afternoon or evening after flying west.
Follow local times for meals and sleep as soon as possible.
Keep naps short (around 20 to 30 minutes) and avoid them in the late afternoon.
Be active during the day, and keep the bedroom dark and cool at night.
Avoid using alcohol to help you sleep; it worsens sleep quality.

Does melatonin help with jet lag?

Melatonin is a hormone your body makes in the evening to signal that it is time to sleep. In the UK, melatonin is a prescription-only medicine, and one 3 mg tablet product is licensed for the short-term treatment of jet lag in adults. Some people find it helps them fall asleep at the new local bedtime, although research results are mixed and it is not usually available on the NHS for jet lag.

Points a prescriber will consider include:

It is intended for short courses only, taken at local bedtime, and not taken earlier than 8pm or later than 4am local time.
It can cause drowsiness, so you should not drive or operate machinery after taking it.
It is not recommended in pregnancy or breastfeeding, for under-18s, or for people with some liver, kidney or autoimmune conditions.
It can interact with other medicines, including fluvoxamine, some antibiotics, warfarin, hormonal contraception and HRT.
Food and alcohol should be avoided around the time of the dose.

Melatonin bought online from overseas sellers may not meet UK quality standards, and the dose can vary from the label. A prescriber will decide whether melatonin is appropriate for you after reviewing your health and other medicines.

Do sleeping tablets help jet lag?

Sleeping tablets are not generally recommended for jet lag. They can cause next-day drowsiness and do not reset your body clock. Speak to a pharmacist or doctor if you are struggling.

Frequently asked questions

How long does jet lag last?

Usually a few days. A rough guide is that the body adjusts by about one time zone per day, so recovery is longer after crossing many time zones.

Is jet lag worse flying east or west?

Many people find eastward travel harder, because it requires going to sleep earlier than the body clock wants.

Can children take melatonin for jet lag?

Melatonin is not licensed for jet lag in under-18s. For children, focus on daylight, routines and sleep timing, and ask a pharmacist or GP for advice.

Should I see a clinician before travelling?

It is a good idea if you have a long-term condition, take medicines at fixed times (such as insulin or contraception), or need travel vaccinations or malaria advice.

Key takeaways

Jet lag is a temporary mismatch between your body clock and local time.
Gradually shifting your sleep, timing daylight exposure and staying hydrated are the main ways to reduce it.
Melatonin is prescription-only in the UK and suitable only for some adults, for short periods.
Plan medicine timings across time zones before you travel.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

Planning a long-haul trip from Wigan, Standish, Chorley or Bolton? You can book a travel health consultation at Ready Health to discuss jet lag, your medicines and any vaccinations you may need.

Jet Lag: Symptoms, Prevention Tips and When to Get Advice