Health Library

Deep Vein Thrombosis


Deep vein thrombosis (DVT) is a blood clot in a vein deep in the body. A blood clot is a buildup of red blood cells, proteins, and other cells in a vein. As the clot grows, it blocks blood flow in the vein.

In DVT, blood clots happen most often in the legs and pelvis. They can also happen in other parts of the body.

DVT can lead to serious and life-threatening problems such as a pulmonary embolism.

Deep Vein Thrombosis
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DVT can be caused by:

  • Injury to a vein
  • Slow blood flow and blood pooling in a vein
  • Blood clotting problems

Risk Factors

The risk of DVT increases with age. Other things that raise the risk are:


DVT does not always cause symptoms. When symptoms happen, they may be:

  • Pain in the affected area
  • Swelling of a leg or arm
  • Tenderness along the vein, especially near the thigh
  • Redness, paleness, or blueness of the affected leg or arm

Some may not have any symptoms until the clot moves to the lungs. This condition is called a pulmonary embolism.


The doctor will ask about symptoms and past health. A physical exam will be done.

To diagnose DVT, the doctor may test blood and blood flow with:

  • Blood tests
  • Compression venous ultrasound
  • Venography


The goals of treatment are to:

  • Stop the clot from growing
  • Dissolve the clot, if possible
  • Prevent other problems, such as a pulmonary embolism and more clots

Treatment options are:

  • Blood thinning medicine by IV or shots—to prevent DVT. It may be used for a long time.
  • Medicine delivered to the site using a catheter and x-rays—to dissolve clots. It is given for clots that are large, serious, or in an arm.
  • Compression stockings—worn on the legs to improve blood flow.

For large and serious clots, surgery may be done, such as:

  • Thrombectomy—the clot is taken out.
  • Inserting an inferior vena cava filter—a small device is placed in a vein. It prevents a blood clot from going to the lungs.


To help lower the risk of DVT:

  • Do not sit for long periods of time. Get up and move around.
  • If confined to bed, move arms and legs often. Change positions at least every 2 hours.
  • Carefully follow any treatment if you had a DVT before.


American Heart Association

American Venous Forum

Canadian Resources

Health Canada

Heart and Stroke Foundation of Canada


Deep vein thrombosis (DVT). EBSCO DynaMed website. Available at:

Deep vein thrombosis. Ortho Info—American Academy of Orthopaedic Surgeons website. Available at:

Di Nisio M, van Es N, et al. Deep vein thrombosis and pulmonary embolism. Lancet, 2016; 388(10063): 3060-3073.

What is venous thromboembolism? Centers for Disease Control and Prevention website. Available at: