What is jet lag?

Travel can take its toll when your body clock is disrupted.

By Donna Fleming


Jet lag is caused when you fly long distance and your internal clock or circadian rhythms – which tell your body when to sleep and when to stay awake – end up out of sync with the time zone you are in. Jet lag can lead to:
  • Daytime fatigue
  • Disturbed sleep
  • Difficulty concentrating or functioning normally
  • Bowel irregularities, such as diarrhoea or constipation
  • Generally feeling unwell
  • Aching muscles
The woozy sensation you get after a long-haul flight normally passes after you’ve had a sleep, but it may take a couple of days before you stop feeling extremely tired and waking up at odd hours of the night. If you are a frequent flyer you may find it harder to get over the symptoms.


It’s not generally associated with fainting, but if you’re jet lagged and you get up suddenly from a lying or sitting position, you could feel faint, especially if you are already prone to low blood pressure or dizzy spells. There have also been cases where disruption to circadian rhythms has been linked to heart attacks and strokes, but these are extremely rare. One of the greatest risks of jet lag is being so tired that it affects your ability to drive or operate machinery. After a long-haul flight, try not to drive until you’ve had at least one good night’s sleep, and avoid driving long distances until you are well rested.


  • Get a good night’s sleep before you travel. Being sleep-deprived to start with makes jet lag worse.
  • Set your watch to the time at your destination when you get on the plane and try to get in sync with that time. For example, when it is night time at your destination, try to sleep on the plane. Earplugs and eye masks can help to block out noise and light. If it is daytime where you are going, then resist the urge to sleep, or restrict yourself to a nap.
  • Stay hydrated. While there is some contention over whether dry cabin air really does dehydrate passengers, drinking plenty of water before, during and after your flight won’t hurt. If you do get dehydrated it can make jet lag feel worse.
  • Avoid alcohol and caffeine. These can lead to dehydration and also affect your sleep.
  • Get into a routine in your new time zone as soon as possible. Eat at the right times and, if you arrive in the morning, stay up until dark. If you need a nap, set an alarm or have someone wake you after 45 minutes. Any longer, and you will get into REM sleep and feel seriously groggy when you wake. If you sleep in the middle of the day for five or more hours, your body clock will be well and truly out of sync.
  • Melatonin is a hormone, available as a supplement, that can help reset your body clock. Studies show that those who take it may experience less fatigue and get back into their normal sleep patterns more quickly. However, other research has found up to a quarter of people notice no benefits, and around 10% have side effects such as headaches. Also, little is known about its long-term effects.
  • undefined: Donna Fleming

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