Sitting for long periods, particularly for over five hours in an aircraft, bus, train or car can lead to a condition called deep vein thrombosis or DVT. The combination of cramped seating, immobility, dehydration and reduced oxygen pressure at high altitude can cause blood clots to form, typically in the veins of the legs. If a piece of a clot breaks off and travels to the lungs the consequences can be severe, even fatal. 

Some travellers are more at risk of DVT than others, particularly those who:

  • Have had DVT previously
  • Smoke
  • Are overweight or obese
  • Are pregnant
  • Are aged 40 or older
  • Have major varicose veins
  • Have had surgery recently
  • Have cancer
  • Have Systemic Lupus Erythematosus (SLE)
  • Use a contraceptive pill or hormone replacement therapy

Prevention and Treatment

Travellers who have previously had a DVT may be advised to take anti-coagulant medication before the flight to reduce their risk.

DVT Prevention Tips

  • Exercising regularly during the journey.
  • Avoiding sitting with your legs crossed.
  • Drinking plenty of water or juice during the flight to maintain hydration.
  • Avoiding excessive alcohol, tea, or coffee as they cause dehydration.
  • Wearing properly fitted compression stockings if you are at a high risk of DVT or tend to suffer from leg swelling during flights. Compression stockings improve blood flow from the legs and prevent swelling.