The diagnosis of deep vein thrombosis (DVT) should be suspected when there is new swelling and pain in just one leg. Although muscle injury, bleeding into a leg muscle or a ruptured cyst behind the knee can cause similar symptoms, it is often difficult to make the diagnosis simply by examining the leg.

The most widely used diagnostic test is an ultrasound of the leg. Any doctor who suspects a possible DVT can order an ultrasound.

If a DVT is confirmed by ultrasound or other testing, treatment can be directed by a doctor trained in internal medicine or family practice. In more complicated cases, a doctor with special expertise in clotting problems can be consulted. Often one or two doctors on staff in a hospital have developed extra expertise and experience in treating DVT and associated problems such as pulmonary emboli (blood clots that break off from the veins and travel to the lungs).