Deep vein thrombosis (DVT)

When you sit still for long periods of time you increase your risk of blood clots (called deep vein thrombosis). Deep vein thrombosis is a particular risk for people travelling on long journeys.

Travel and blood clots

When you sit still for long periods of time you increase your risk of blood clots. This is because sitting still slows the blood flow from your legs back to your heart. You are at risk of blood clots on any long car, bus or train trip, not just planes. Clots can form on journeys as short as 3 hours.

If a clot passes up the veins and to the heart it can become stuck in one of the blood vessels supplying the lungs. This can cut off the oxygen supply to the body. This is known as a pulmonary embolism. It can be fatal.

Restricted leg room can slow the flow of blood even more, particularly when the back of the seat in front is pressing on your shins.

People at risk

Deep vein thrombosis is a higher risk if you:

  • have had a deep vein thrombosis or blood clots before
  • have been unwell or had an operation recently
  • are older
  • are pregnant or have recently given birth
  • take the pill or hormone replacement
  • smoke tobacco.


Deep vein thrombosis usually affects one leg (occasionally both). The symptoms are usually:

  • swelling and warmth in the skin of your lower leg, ankle, foot
  • pain and tenderness in your calf, and sometimes up to your thigh
  • change in the colour of your lower leg for example, the veins becoming more prominent (darker and raised) and sometimes the skin being red, blue or pale compared to the other leg.

If you think you might have a deep vein thrombosis:

  • see your healthcare provider, or
  • call Healthline 0800 611 116 for advice.


Reduce your chance of deep vein thrombosis by following these tips.

  • If flying, try to get a seat with extra leg room, such as one next to an emergency exit.
  • Drink plenty of water to reduce dehydration (which increases the risk of blood clots), especially if you are drinking alcohol or drinks containing caffeine.
  • Stand up and walk around as often as you can.
  • While seated, exercise your calf muscles every half-hour by flexing and rotating your ankles for a few minutes.
  • Sleep only for short periods and do not take sleeping pills that could keep you motionless in your seat for hours.
  • Wear support stockings if you are flying.
  • Avoid wearing tight clothing around your waist.
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