Deep venous thrombosis

Latest update: - Authors: Mieke Croughs, Ula Maniewski-Kelner

A deep vein thrombosis (DVT) is a blood clot located in a deep vein, usually in the legs. 

A DVT is usually caused by a combination of different factors. One of these factors is a period of reduced activity, for example an aeroplane or car journey longer than four hours. The longer the flight or journey, the greater the risk. A DVT usually occurs shortly after the journey, but the risk remains elevated up to eight weeks after the journey.   

DVT occurs mainly in people with pre-existing risk factors, such as:  

  • obesity (BMI > 30)  
  • a previous thrombosis   
  • pregnancy  
  • active cancer 


Prevention during a flight of 4 hours or more.


Wear loose, comfortable clothing.

Getting up

Ask for an aisle seat so that you can get up easily.

Leg room

Ensure that you have enough space in the area under the seat in front of you, so that you can move your feet.


Change position regularly.


Perform exercises for your legs and feet several times per hour.

Walk around

Get up regularly and walk around.

Increased risk?

If you have any of the risk factors for DVT, discuss with your doctor whether the following additional measures are necessary: 

  • Support stockings up to the knee.
  • An anticoagulant injection two to six hours before the flight or an oral anticoagulant (NOAC).
  • Acetylsalicylic acid (aspirin) does not help in this context.

Additional information for doctors

Deep venous thrombosis and travelling


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