What jet lag is
Your body runs on an internal clock of roughly 24 hours that controls sleep, alertness, hunger and digestion. Daylight is the main signal that keeps it set. When you cross several time zones quickly, the clock falls out of step with the day around you. The result can be poor sleep, daytime tiredness, trouble concentrating, headaches and an upset stomach.
It usually takes a few days to adjust. A common rule of thumb is about a day for each time zone crossed, though people vary a lot. Many people find flying east harder than flying west, because it means going to sleep earlier than the body wants.
Use light deliberately
Light is the strongest tool you have for resetting your body clock.
- After flying east, get bright light, ideally daylight outdoors, in the morning at your destination, and keep evenings dim.
- After flying west, get daylight in the late afternoon and early evening, which helps you stay up later.
- On long trips across many zones, the best timing can be less obvious. A clinician or a reputable travel health source can help you plan.
Even a 20 or 30 minute walk outside at the right time of day helps, and it also gets you moving after the flight.
Shift sleep and meals
- In the few days before a big eastward trip, go to bed and get up a little earlier. Before a westward trip, a little later.
- On the plane, set your watch to destination time and try to sleep or stay awake to match it.
- Eat meals at local times as soon as you arrive. Meal timing also helps reset the body clock.
- If you must nap on arrival, keep it short, around 20 to 30 minutes, and before mid-afternoon.
Caffeine, alcohol and sleep aids
Caffeine in the morning can help you stay alert, but avoid it in the hours before you plan to sleep. Alcohol may make you drowsy, yet it tends to disturb sleep later in the night and adds to dehydration on a flight.
Some travelers use melatonin or sleep medication. Talk to a doctor or pharmacist before you try either. Rules on melatonin differ by country, and sleep medicine can interact with other medicines or leave you groggy in a meeting.
Very short trips
For a trip of one or two days, trying to adjust may not be worth it. Some travelers stay roughly on home time instead: they schedule meetings for the hours when they would naturally be alert, and sleep when their body expects to. This works best when the time difference is small or the trip is very short.
Schedule around the jet lag
| Trip | Approach many travelers use |
|---|---|
| 1 to 3 hours difference | Adjust on arrival. Keep the first evening quiet. |
| 4 to 7 hours, short stay | Arrive a day early for important meetings. Book key sessions for the time you would be alert at home. |
| 4 to 7 hours, a week or more | Shift sleep a little before leaving, use light on arrival, keep the first day light. |
| 8 hours or more | Allow at least one recovery day before anything important. Ask for advice if you have a health condition. |
If you can choose meeting times, avoid putting the most important one in your body's "night", which is often the early afternoon after a long eastward flight.
Coming home
Jet lag works in both directions. If you can, keep the first day back free of big decisions and long drives. Driving while very tired is risky, so consider a taxi or public transport home from the airport after an overnight flight. The health guide covers sleep and wellbeing on the road more generally.
Does jet lag get easier with frequent travel?
Frequent travelers often get better at managing it, because they learn what helps them. The body clock itself still needs time to shift, so the basics of light, sleep and meal timing still apply.