What do I need to know before I travel?
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Deep Vein Thrombosis


Long distance travel is a risk factor in the development of blood clots. The risk is not confined to air travel; it increases with the duration of travel and is more common in those with pre-existing risk factors.

Prolonged periods of immobility can lead to slow blood flow in the veins which increases the risk of developing a blood clot within a deep vein in the body; this is called deep vein thrombosis (DVT). Blood clots most commonly form in the legs. If parts of the clot break off and travel to the lungs, this can block blood vessels and is called pulmonary embolism (PE) which is a potentially life threatening condition.

Although the absolute risk of developing DVT or PE after a long haul flight is very small, the risk is increased if you have pre-existing risk factors.

Pre-Existing Risk Factors

If you have any of the following risk factors, you may be at greater risk of DVT or PE and should be assessed by your GP prior to travel:

  • a history of DVT or PE
  • blood clotting abnormalities
  • cancer, whether untreated or currently on treatment
  • pregnancy or it is less than 6 weeks since delivery
  • recent surgery
  • recent serious injury or trauma
  • heart or lung disease
  • a close family member has a history of DVT or PE
  • you are over 60 years of age
  • if you are taller than 1.90m or shorter than 1.60m (adult)
  • varicose veins
  • mobility problems
  • obesity
  • you are taking combined oral contraceptives (the pill) or hormone replacement therapy (HRT)

​Preventive Measures

General advice

  • Move around as much as possible.
  • Choose an aisle seat where feasible as this is known to encourage moving around during the journey .
  • Carry out calf muscle exercises:
    • flex and extend your ankles to encourage blood flow.
  • Try to avoid placing cabin baggage where it can restrict your leg movement.
  • Avoid excessive alcohol consumption and the use of tranquilisers or sleeping tablets as this may discourage you from moving.
  • Keep well hydrated as this this can encourage walking to toilet.
  • Seek urgent medical attention if you develop:
    • swollen, painful legs especially if one is more so than the other
    • breathing difficulties.

Aspirin therapy

  • It is now accepted that there is no place for aspirin in the prevention of travel related DVT or PE.

Anti-embolism stockings

If you are at an increased risk of DVT or PE, anti-embolism stockings (AES) might be recommended to reduce your risk. You should discuss this with your travel health advisor or GP. AES are sometimes called graduated compression stockings (GCS):

  • Ensure you buy the correct type and size of stocking and know how to wear them correctly.
  • If you have varicose veins, wearing AES can slightly increase your risk of an inflamed vein near the surface of the skin (this is called superficial thrombophlebitis).
  • If you require a higher level of compression than basic AES provide, you must be measured and fitted by a trained individual:
    • incorrectly fitting AES can increase your risk of DVT or PE.

Low molecular weight heparin

Low molecular weight heparin can be considered for those at higher risk of developing DVT (see above). This treatment is administered by injection and must be prescribed by your GP or hospital specialist and used under their direction.

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