flying and reducing the risk of pulmonary embolism (PE)

Last reviewed 07/2021

Travellers' thrombosis is the occurrence of venous thromboembolism (VTE) (deep vein thrombosis (DVT) or pulmonary embolism (PE)) related to travel.

  • unfortunately, good quality randomised controlled trials are lacking in this area (1,2)
    • according to a research, all forms of transport involving a journey of 4 hours or more are associated with DVT
    • the risk of flight related DVT is increased in both shorter and taller individuals and in the  overweight and is associated with location in a window seat
    • risk is also increased in combined oral  contraceptive pill use and carriage of factor V Leiden
    • there is no evidence to suggest that dehydration is an important factor

  • the UK Department of Health (DH) recommends that patients with a personal or family history of VTE or clotting abnormalities, a history or current treatment of cancer, those who have suffered a stroke or have had recent major surgery, obtain medical advice before travelling.
    • the DH has also issued further specific advice to travellers (3)
      • Before the trip
        • some experts advise patients who have had a hip or knee replacement to avoid long haul flights for three months
        • patients who are in a high-risk group (including women taking the pill or HRT) may wish to consider the use of elastic stockings
      • During the trip
        • guidance for the avoidance of deep vein thrombosis and venous thromboembolism (4)

          Blood clots - Deep venous thrombosis (DVT) and venous thromboembolism (VTE) Risk criteria Risk reduction advice for passengers
          Low Risk

          -no history of DVT / VTE

          -no recent surgery (four weeks)

          -no other known risk factor

          Keep mobile.Drink plenty of non alcoholic drinks.Do not smoke. Avoid caffeine and sedative drugs.
          Medium Risk

          -history of DVT/VTE

          -surgery lasting more than 30 minutes between 4 and 8 weeks ago

          -known clotting tendency

          -pregnancy -obsesity (BMI.30)

          As for 'low risk'with addition of compression stockings
          High Risk

          -previous DVT with known additional risk including known cancer

          -surgery lasting more than 30 minutes within the last 4 weeks

          As for moderate risk but sub cutaneous injections of Enoxoparin 40 mg before the flight and on the following day
      • After the trip
        • if you develop swollen, painful legs, especially if one is more affected than the other, or if breathing difficulties occur, see a local doctor urgently or visit the nearest accident and emergency department.

There is also guidance suggesting that individuals with a high risk of developing VTE, who wish to fly, should wear graduated elasticated compression stockings.

  • in the general population, there is evidence that prophylactic use of graduated compression stockings during air travel reduces the rate of flight related DVT (5,6)

Also a review of air travel and venous thromboembolism stated (7):

  • for the majority of healthy air travellers the risk of deep vein thrombosis or pulmonary embolus is very small
  • risk of symptomatic venous thromboembolism increases with flight duration
  • most air travellers who develop thrombosis have additional risk factors for venous thromboembolism
  • patients at risk of venous thromboembolism should be warned of the dangers of long haul flights
  • compression stockings reduce the incidence of deep vein thrombosis
  • low molecular weight heparin is effective, but should only be used in those at highest risk
  • there is currently no evidence that aspirin is effective


  • the use of AES for prevention of VTE during and after long-haul travel is not routinely recommended. When used, care should be taken to ensure an appropriate fit