Jet lag refers to a range of symptoms experienced while adapting to a different light-dark schedule following a flight to a new time zone.

It can affect people of all ages and is the result of your internal body clock not being able to adjust immediately to a new time zone.

Jet lag can disturb your sleep at night and make you feel drowsy and lethargic (lacking in energy) during the day. It can also sometimes cause digestion problems.

Crossing seven to 12 time zones usually results in more severe jet lag than crossing three to six time zones. Crossing one or two time zones doesn't usually cause any problems.

People usually report more severe jet lag for easterly flights compared with westerly flights across the same number of time zones. 

Jet lag isn't the same as general travel fatigue and can't be cured by certain types of aircraft, a more comfortable seat, “speedy-boarding” or the class of travel.

Read more about the symptoms of jet lag.

What causes jet lag?

The world is divided into 24 different time zones. Your body's natural 24-hour clocks control 24-hour circadian rhythms, which are disrupted after crossing time zones.

Your body clocks influence your sleeping and waking pattern, as well as circadian rhythms in:

  • appetite
  • digestion
  • bowel habits
  • urine production
  • body temperature
  • blood pressure

Your body clocks are set to your local time by light and social interaction, so that you're prepared for becoming active in the morning and for going to sleep at night.

If you travel across time zones, it can take a while for your body clocks to adjust to a new light-dark schedule and daily routine at your destination.

Read more about the causes of jet lag.

Treating jet lag

Jet lag can be a problem if, like pilots and cabin crew, you fly frequently across three or more time zones. However, there's little evidence to suggest that long-term human health is affected by jet lag. For example, the risk of most cancers is lower in commercial airline crew.

In most cases, jet lag symptoms pass after a few days without the need for treatment. Not many proposed treatments have been tested properly in clinical trials. The advice below is a "common-sense" approach that might help reduce the effects of jet lag.

When you arrive at your destination:

  • establish a new routine - eat and sleep at the correct times for your new time zone, not at the time you usually eat and sleep at home
  • avoid napping as soon as you arrive - even if you're tired after a long flight, staying active until the correct time to sleep at your destination will help your body adjust quicker
  • spend time outdoors - natural daylight will help your body adjust to a new routine following most flights

Read more about treating jet lag.

Preventing jet lag

It's not possible to prevent jet lag, and evidence about various treatments isn't very robust.

However, there are some things that might be useful to help reduce its effects, such as changing your sleep routine a few days before departure and making sure you get enough sleep before you travel.

Read more about preventing jet lag

Page last reviewed: 24/11/2014

Next review due: 24/11/2017