Why Jet Lag Happens When You Travel
Jet lag happens when you travel across time zones faster than your body clock can adjust. Your body runs on an internal clock called the circadian rhythm, which controls sleep, hunger, temperature, and energy levels. When you fly long distance, especially east or west across several time zones, your internal clock is still running on your home time even though the local time is different.
This is why you might arrive somewhere in the morning and feel exhausted, or wake up wide awake at 3am. Your body still thinks it is in a different time zone.
Jet lag is usually worse when travelling east because you are effectively shortening your day and trying to go to sleep earlier than your body expects. Travelling west is usually easier because you are extending your day and going to bed later, which is easier for most people to adjust to.
The number of time zones crossed also makes a big difference. Travelling across one or two time zones usually causes very little jet lag, but crossing five or more time zones often causes noticeable symptoms such as fatigue, poor sleep, headaches, irritability, and difficulty concentrating.
Jet lag is not dangerous, but it can make the first few days of a trip much less enjoyable if you do not prepare for it properly.
How Long Jet Lag Lasts After a Long Haul Flight
Jet lag does not disappear immediately after you arrive. A common rule used by frequent travellers and airline crews is that your body adjusts by roughly one time zone per day.
For example, on eastbound long-haul routes:
- UK to New York (5 hours difference) → about 3–5 days to adjust
- UK to Dubai (4 hours difference) → about 2–4 days
- UK to Singapore (8 hours difference) → about 5–8 days
- UK to Australia (10+ hours difference) → about 7–10 days
- New York to Tokyo (14 hours difference) → about 8–10 days
The same one-time-zone-per-day rule applies whatever your starting point, so a traveller flying Sydney to London or Los Angeles to Dubai can expect a similarly long adjustment period. This is why short trips across many time zones can be particularly tiring, because your body never fully adjusts before you travel back again.
Symptoms of jet lag can include tiredness during the day, waking up very early, difficulty falling asleep, reduced appetite, stomach issues, headaches, and difficulty concentrating. Many travellers feel awake when they should be sleeping and sleepy when they should be exploring, which is the classic jet lag problem.
The good news is that there are several ways to reduce jet lag and adjust to a new time zone faster.
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One of the best ways to reduce jet lag is to start adjusting your sleep schedule before you travel. If you are travelling east, try going to bed earlier for a few days before departure. If travelling west, try staying up later and waking up later.
Even shifting your sleep schedule by one hour per day before travelling can make a big difference when you arrive. Preparing your body before the flight is one of the most effective ways to reduce jet lag.
Sleep is very important before long haul flights. Starting a trip already tired makes jet lag much worse. Try to get a good night’s sleep before travelling rather than staying up late packing or travelling to the airport.
Hydration is also important because flying is very dehydrating, and dehydration makes jet lag symptoms worse. Drink plenty of water the day before and during the flight.
Many frequent travellers also adjust their watch to the destination time as soon as they board the plane. This helps mentally switch into the new time zone and encourages you to sleep and eat according to destination time rather than departure time.
Preparing properly before travelling can reduce jet lag significantly, especially on very long flights.
How To Reduce Jet Lag During the Flight
What you do on the plane can make a big difference to how you feel when you arrive. The most important thing is to try to sleep according to the time at your destination, not according to your departure time.
If it is nighttime at your destination, try to sleep on the plane. If it is daytime at your destination, try to stay awake, watch films, read, or walk around the cabin.
Drinking water regularly during the flight is very important because cabin air is very dry. Avoid drinking too much alcohol or caffeine because both can disrupt sleep and increase dehydration.
Eating light meals rather than heavy meals can also help your body adjust more easily. Some travellers also use eye masks, neck pillows, and noise-cancelling headphones to improve sleep on long flights.
Moving around the cabin occasionally helps circulation and reduces stiffness, especially on flights longer than six hours.
Think of the flight as the first part of adjusting to the new time zone, not just transport from one place to another.
How To Recover From Jet Lag Faster After You Arrive
Once you arrive at your destination, the most important thing you can do is switch immediately to local time, even if you are tired.
If you arrive in the morning, try to stay awake until evening. If you arrive in the evening, try to go to bed at a normal local bedtime. Short naps can help, but long naps often make jet lag worse because they confuse your body clock further.
Sunlight is one of the most powerful ways to reset your body clock. Spending time outside in daylight helps your body adjust to the new time zone faster. This is why going for a short walk outside after arriving can actually help reduce jet lag.
Eating meals at local times also helps your body adjust because digestion is linked to your body clock. Even if you are not very hungry, eating small meals at normal local meal times helps your body adapt.
Light exercise such as walking can help with jet lag, but heavy exercise on the first day is not recommended if you are very tired.
The key rule is simple: sleep at night, stay awake during the day, and get sunlight as soon as possible.
Melatonin, Sleeping Tablets and Jet Lag Remedies
Many travellers look for medication or supplements to help with jet lag, especially on very long flights. The most commonly used jet lag supplement is melatonin, which is a hormone that helps control your sleep cycle.
Melatonin is often used to help people fall asleep at the correct local bedtime when travelling across time zones. It is usually taken in the evening at the destination for a few days after arrival. Some travellers also take it on the plane if they need to sleep during the destination night time. Melatonin is available over the counter in some countries and by prescription in others.
Sleeping tablets are sometimes used on long haul flights, but they should be used carefully. Sleeping tablets may help you sleep on the plane, but they do not actually fix jet lag, they only help with sleep during travel. They can also make you feel groggy when you arrive and should not be combined with alcohol.
Caffeine can be useful for staying awake during the day when you arrive, but it should be avoided in the evening because it can make it harder to sleep at the correct local bedtime.
Some travellers also find that light exercise, walking outside, and eating meals at local times are just as effective as medication for reducing jet lag. In many cases, sunlight and sleep timing are more effective than any tablet.
The most important thing is not medication, but adjusting your sleep and light exposure to match the new time zone as quickly as possible.
Jet Lag East vs West – Which Direction Is Worse?
Jet lag is usually worse when travelling east than when travelling west. This is because travelling east shortens your day, while travelling west makes your day longer.
For example, if you fly from London to New York, the local time is earlier than your body clock expects, so you simply stay awake longer and go to bed later. Most people find this easier to adjust to.
However, if you fly from London to Dubai, Singapore, or Australia, you are travelling east and your body needs to sleep earlier than it expects, which is more difficult. This is why many travellers find flights to Asia and Australia cause worse jet lag than flights to North America.
Airline crews and frequent flyers often say:
West is best, east is a beast.
This is not always true for everyone, but in general eastbound travel causes more jet lag than westbound travel.
When travelling east, it is helpful to go to bed earlier for a few days before travelling. When travelling west, it is helpful to go to bed later before travelling.
Planning sleep times before travel can significantly reduce jet lag symptoms.
Simple Jet Lag Strategy That Works For Most Travellers
If travellers remember only a few things about jet lag, this simple strategy works for most long haul trips.
Before travelling, try to adjust your sleep schedule slightly towards your destination time. During the flight, sleep if it is night at your destination and stay awake if it is day at your destination. Drink plenty of water during the flight and avoid too much alcohol.
After arriving, switch immediately to local time. Stay awake during the day, get sunlight, eat meals at local times, and go to bed at a normal local bedtime. Short naps are fine, but long naps should be avoided because they make jet lag last longer.
Sunlight, sleep timing, and hydration are the three biggest factors that determine how quickly you recover from jet lag.
Most travellers who follow these simple rules recover from jet lag much faster than those who just sleep whenever they feel tired.
Rupert’s Handy Travel Tips
Long haul flights can leave you exhausted for the first few days of your trip, but a few simple habits can help reduce jet lag and get you enjoying your destination faster.
- Switch to destination time on the plane: Sleep and eat according to where you’re going, not where you left.
- Drink plenty of water: Flying is very dehydrating and dehydration makes jet lag worse.
- Get sunlight when you arrive: Daylight helps reset your body clock faster.
- Avoid long naps: Short naps are fine, but long naps make jet lag last longer.
- Stay awake until local bedtime: This is one of the fastest ways to adjust.
Want to meet the reindeer behind our travel tips? Find out more in our page Who is Rupert?.
Frequently Asked Questions About Jet Lag
How long does jet lag last?
Jet lag usually lasts one day per time zone crossed, although good planning and sleep timing can reduce this.
Is jet lag worse flying east or west?
Jet lag is usually worse flying east because you are shortening your day and trying to sleep earlier than your body expects.
Should I sleep on the plane?
You should sleep on the plane if it is night time at your destination. If it is daytime at your destination, try to stay awake.
Does alcohol make jet lag worse?
Yes. Alcohol disrupts sleep and dehydrates the body, which makes jet lag worse.
Does melatonin help jet lag?
Melatonin can help some travellers fall asleep at the correct local time, especially when travelling across many time zones.
Further Reading & Related Travel Guides
Travelling long distances and visiting new destinations can affect your body in different ways. These guides will help you stay healthy, safe and comfortable while travelling. If your trip also takes you somewhere high up, our altitude sickness guide explains how to recognise the symptoms and prevent and treat them, and if you are heading somewhere hot, our sunstroke and heatstroke guide covers the warning signs and how to stay safe in the sun.
Long flights are often followed by ferries or cruises, so it is worth reading our seasickness guide for tips on avoiding motion sickness at sea, and travellers heading to rural or wilderness regions after a long-haul flight may also want to check our hantavirus travel guide.
Beyond these, our food and drink safety guide helps you avoid food poisoning and stomach problems, our travel insurance guide explains what cover you need for medical emergencies, cancellations, delays and lost luggage, and an eSIM keeps you connected for maps, transport apps and bookings without expensive roaming charges.
