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Deep vein thrombosis (DVT) is the formation of a blood clot in a vein deep under the skin.
The most common sites of deep vein clots are the lower leg and thigh. They can also occur in the pelvis and arm.
Causes of a thrombus (blood clot) include slow blood flow, an injury to the lining of a vein, or having blood with an increased tendency to clot.
Limited movement can cause slow blood flow, which increases the risk of DVT. Limited activity can occur with prolonged bed rest after surgery or because of illness.
Injury of a deep vein from fracture, surgery, or severe muscle injury can lead to DVT.
Estrogen in birth control pills or hormone therapy makes blood more likely to clot. Clotting risk is also higher during pregnancy and for up to 6 weeks after giving birth because of increased estrogen.
Cancer and some inherited (genetic) blood disorders increase the risk of blood clots.
Certain long-term medical conditions including heart disease and inflammatory bowel disease increase the risk of DVT.
Other factors that increase the risk of DVT are older age, being overweight or obese, having had DVT in the past, and having a family member who has had DVT.
The most common symptoms of DVT occur at the site of the clot. They include swelling, warmth, pain or tenderness, and redness of the skin. Deep vein thrombosis can also occur with no symptoms.
A blood clot or part of a blood clot in a deep vein can break off and travel through the bloodstream. An embolus (loose clot) that reaches the lungs is called a pulmonary embolism (PE).
Most PEs are treatable, but a large PE can completely block blood flow to the lungs and is life threatening. Symptoms of a PE can include sudden shortness of breath, pain with deep breathing, fast heartbeat, coughing up blood, lightheadedness, and fainting.
Anticoagulants (blood thinners) are used to treat DVT. These medicines make it harder for the blood to clot, so they prevent a deep vein thrombus from becoming larger. Compression stockings can help reduce pain and swelling from DVT.
If you are sitting for a long period (such as while traveling), do simple leg exercises such as stretching and flexing your feet. It may also help to stand up and walk around periodically. The same advice applies if you are confined to bed because of illness or surgery. After bed rest of a few days or after surgery, becoming active as soon as possible may help prevent clots. If you are at increased risk of DVT, your doctor may recommend taking an anticoagulant or using compression stockings. Having an active lifestyle and maintaining a healthy weight also reduce the risk of DVT.
Centers for Disease Control and Preventionwww.cdc.gov/ncbddd/dvt/index.html
National Heart, Lung, and Blood Institutewww.nhlbi.nih.gov/health/health-topics/topics/dvt
To find this and previous JAMA Patient Pages, go to the Patient Page link on JAMA’s website at jama.com. Many are available in English and Spanish. A Patient Page on pulmonary embolism appeared in the February 5, 2013, issue; one on blood thinners in the December 18, 2013, issue; and one on air travel–related DVT and PE in the December 19, 2012, issue.
Sources: Centers for Disease Control and Prevention
National Heart, Lung, and Blood Institute
Wells PS, Forgie MA, Rodger MA. JAMA. 2014;311(7):717-728.
Topic: Vascular Disease
Thompson AE. Deep Vein Thrombosis. JAMA. 2015;313(20):2090. doi:10.1001/jama.2015.4761