Last updated: October 2026
Jet lag is the poor sleep, daytime tiredness and foggy head you get when your body clock is out of step with a new time zone. The worst usually eases within a few days, but full adjustment takes about a day per hour of time difference flying east, and a little less flying west.
Jet lag symptoms
Fly across several time zones and the clock on the wall jumps, but your body clock does not. Until the two line up, your sleep, hunger and alertness run on home time.
The NHS lists these common symptoms:
- difficulty falling asleep at bedtime and waking up in the morning
- tiredness and sleepiness during the day
- poor quality sleep
- trouble concentrating and remembering things
- indigestion, feeling sick, constipation or changes in appetite
- feeling mildly anxious
The US CDC says symptoms start within one to two days of travel across at least two time zones. A short hop to Spain or Greece rarely causes it; a flight to New York, Dubai or Bangkok often does. If you’re already short on sleep before you go, it hits harder: see sleep deprivation.
How long does jet lag last?
The NHS says jet lag usually improves within a few days as your body adjusts. Full adjustment takes longer. The CDC puts the average body clock shift at about 1 hour a day after flying east and about 1.5 hours a day after flying west, so the bigger the time difference, the longer it takes.
| From the UK to | Time difference | Direction | Rough time to fully adjust |
|---|---|---|---|
| New York, Orlando, Toronto | 5 hours behind | West | About 3 to 4 days |
| Los Angeles, Las Vegas, Vancouver | 8 hours behind | West | About 5 to 6 days |
| Dubai | 3 to 4 hours ahead | East | About 3 to 4 days |
| Thailand | 6 to 7 hours ahead | East | About 6 to 7 days |
| Japan | 8 to 9 hours ahead | East | About 8 to 9 days |
| Sydney | 9 to 11 hours ahead | East | Up to 9 to 11 days |
These are rough figures from the CDC averages, and time differences shift by an hour when clocks change. Many people feel mostly normal well before they are fully adjusted.
Remember the trip home too. Coming back from the USA or Canada to the UK is an eastward flight, which is why so many people find the return leg worse than the outbound one.
Jet lag east vs west: why flying east is harder
For most people, jet lag is worse after flying east. The CDC explains why: the natural body clock runs slightly longer than 24 hours, so we find it easier to stay up later than to go to bed earlier.
- Flying west (UK to the Americas) makes your day longer. You need to stay up later and sleep later, which goes with your body’s natural drift. Expect to feel sleepy in the early evening and wake very early.
- Flying east (UK to the Middle East, Asia or Australia, or home from the USA) makes your day shorter. You need to fall asleep before your body is ready. Expect to lie awake at bedtime and struggle to get up.
Your chronotype plays a part too. Natural night owls tend to cope better heading west, while early birds often find eastward trips a little easier.
How to beat jet lag: before, during and after your flight
Before you fly
- Shift your sleep: the CDC suggests moving bedtime by 1 hour a day for 2 to 3 days before you travel: earlier if you’re flying east, later if you’re flying west. Our sleep calculator helps you plan the new times, and how to wake up early has tips for the earlier mornings.
- Start rested. The NHS advises getting plenty of rest before you go.
- Choose your arrival time if you can, so you land with daylight ahead of you and time to settle before anything important.
On the plane
- Set your watch and phone to destination time as you board, and eat and sleep to it where you can.
- Sleep if it’s night at your destination. An eye mask and earplugs help.
- Drink plenty of water, and get up to stretch and walk around the cabin.
- Go easy on alcohol and caffeine. The NHS says both can make jet lag worse.
When you land
- Switch to local time straight away for meals, bedtime and waking.
- Get outside in daylight. The NHS says this helps your body clock adjust.
- Stay up until a sensible local bedtime, then set an alarm so you don’t oversleep. If you struggle to drop off, try the techniques in how to fall asleep fast.
- Keep the first day or two light if you can.
Short trips
For a trip of only 2 or 3 days, the NHS suggests keeping your usual eating and sleeping times rather than adjusting twice. The CDC gives similar advice for trips under 2 days.
Light, caffeine and naps
Timed light exposure
Daylight is the strongest signal for your body clock, and timing matters:
| Flying east | Flying west | |
|---|---|---|
| Seek light | Morning | Evening |
| Avoid bright light | Evening (sunglasses, blinds) | Early morning |
| Bedtime before you fly | Shift earlier | Shift later |
This is the idea behind jet lag apps and planners. A sports medicine consensus on jet lag recommends following a plan that sets out specific periods of light exposure and light avoidance. Apps work out those windows for your exact flights, which helps most with big time differences.
Caffeine
Caffeine can help you stay alert through your first local day, but timing matters. The CDC notes caffeine has a half-life of about 5 hours and suggests stopping around 6 hours before bed. On an eastward travel day, an early coffee fits; on a westward one, skip the very early cup. If afternoon coffee leaves you flat, read coffee crash.
Naps
The NHS advises against daytime naps after you land, so you sleep properly at night. The CDC says a short nap of 20 to 30 minutes can keep you going if you really need one, but long naps get in the way of night-time sleep. Keep it brief and early: see how to power nap.
Alcohol
A drink may help you nod off, but the CDC says alcohol tends to fragment sleep, and both alcohol and caffeine can leave you dehydrated on a long flight.
Melatonin for jet lag in the UK
Melatonin is the hormone your body releases in the evening as it gets dark. In the UK it is prescription-only. The NHS medicines page says it may help with jet lag symptoms, but the NHS jet lag page says it is not recommended on the NHS for jet lag because there isn’t enough evidence that it works.
The research is more positive than that suggests. A 2002 Cochrane review of 10 trials found that in 9 of them, melatonin taken close to the target bedtime at the destination reduced jet lag after flights crossing five or more time zones. Doses of 0.5mg to 5mg worked similarly, and benefit looked smaller for westward flights.
Timing is crucial. Taken at the wrong time of day, melatonin can make you sleepy and slow your adjustment. The same review flagged possible risks for people with epilepsy and those taking warfarin. So if you think it could help, talk to your GP or a travel clinic before you go rather than buying it online. Read more in melatonin in the UK and our comparison of melatonin vs CBD for sleep.
An evening routine at your destination
A calm, regular wind-down at the new bedtime gives your body clock a consistent cue: dim lights, screens away, the same steps each night. Our sleep hygiene guide covers the basics.
Some people pack a familiar bedtime drink. Our Magnesium Glycinate Sleep Complex is a caffeine-free evening drink with magnesium bisglycinate and citrate, glycine and L-theanine. Magnesium contributes to the reduction of tiredness and fatigue. See the best time to take magnesium for how to fit it into your evening.
Travelling with CBD oil? Rules differ by airline and country, and some countries ban it outright. Check flying with CBD oil and is CBD legal in my country? before you pack.
Jet lag in children
Children’s body clocks respond to the same cues as adults’: daylight, meals and regular sleep times.
- Move bedtime gradually for a few days before you go, if their routine allows.
- Get them outside in daylight on arrival and keep meals on local time.
- Keep familiar bedtime steps, such as a bath, a story and a comforter, so bedtime still feels like bedtime.
Don’t give children melatonin unless a doctor prescribes it. The NHS says specialists only sometimes prescribe it for certain children with longer-term sleep problems. Evopure products are for adults only. If a baby or child is unwell, feverish or not feeding, see a doctor rather than putting it down to jet lag.
Jet lag vs travel fatigue
They often arrive together but are not the same thing. The sports medicine consensus describes travel fatigue as something that follows any long journey, whatever the direction or number of time zones.
| Travel fatigue | Jet lag | |
|---|---|---|
| Cause | The journey itself: cramped seats, dry cabin air, mild lack of oxygen, broken sleep, stress | Body clock out of step with local time |
| Time zones needed? | No. A long flight north to south can do it | Yes, usually two or more |
| How long | Usually eases once you’ve rested | Lasts until your body clock catches up |
| What helps most | Sleep, food and fluids on the journey | Timed light, sleep times and meals at the destination |
Fine after a good night’s sleep? Probably travel fatigue. Still wide awake at 3am on day four? That’s jet lag. For the same body clock clash at home, see shift work and sleep and when the clocks go back.
When to see a GP or pharmacist
Jet lag doesn’t usually need medicine. The NHS says sleeping tablets are only for severe symptoms and short-term use, as they can be addictive. Speak to a pharmacist before using any sleep aid if you take other medicines. See your GP if poor sleep carries on long after you’re home, if you travel so often that you never feel recovered, or if you have symptoms that don’t fit jet lag.
Long journeys of more than 4 hours also raise the risk of a blood clot in the leg (DVT). The NHS says to contact your GP urgently or call 111 if you have throbbing pain or swelling in one leg, and to call 999 if you also feel short of breath or have chest pain.
FAQs
How long does jet lag last?
The worst usually eases within a few days. Full adjustment takes roughly a day per hour of time difference after flying east, and about two thirds of that after flying west.
Is jet lag worse flying east or west?
East, for most people. Flying east shortens your day, so you have to sleep earlier than your body wants. The body clock finds it easier to shift later than earlier.
What is the fastest way to get over jet lag?
Switch to local time as soon as you land, get daylight at the right time of day, stay up until local bedtime, keep naps short and stop caffeine about 6 hours before bed.
Can I buy melatonin for jet lag in the UK?
No. Melatonin is prescription-only in the UK, and the NHS does not routinely recommend it for jet lag. Talk to your GP or a travel clinic if you think it could help.
Should I sleep when I arrive?
Try to stay up until local bedtime. If you can’t, a nap of 20 to 30 minutes earlier in the day is better than a long sleep, which makes the first night harder.
Is jet lag worse coming home from the USA?
Often, yes. Flying from the USA to the UK is an eastward flight, so you need to fall asleep earlier than your body wants, which most people find harder.
Sources
- NHS. Jet lag.
- NHS. About melatonin.
- Riedy SM, Williams SG. Jet lag disorder. CDC Yellow Book 2026 (PMID 41818499).
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. 2002 (PMID 12076414).
- NHS. Deep vein thrombosis (DVT).
- Janse van Rensburg DC, et al. Managing travel fatigue and jet lag in athletes: a review and consensus statement. Sports Med. 2021 (PMID 34263388).
This guide is general information, not medical advice. Evopure makes the Magnesium Glycinate Sleep Complex mentioned in this guide.
