A blood clot in a deep vein, usually in the legs.

Deep vein thrombosis (DVT) can happen when blood doesn't flow or clot properly. The condition is serious. Blood clots in a deep vein can move to the lungs. Some medical conditions raise the risk of DVTs. Not moving the legs for a long time also raises the risk. For example, risk goes up after a long car or airplane ride or bed rest due to surgery.

Symptoms include leg pain or cramping and leg swelling. The skin may change color or feel warm. Some people do not notice symptoms.

Treatments include medications and use of compression stockings.