Diagnosis

To diagnose DVT, your doctor will ask you about your symptoms. You'll also have a physical exam so that your doctor can check for areas of swelling, tenderness or changes in skin color.

The tests you have depend on whether your doctor thinks you are at a low or a high risk of DVT. Tests used to diagnose or rule out a blood clot include:

• D-dimer blood test. D dimer is a type of protein produced by blood clots. Almost all people with severe DVT have increased blood levels of D dimer. A normal result on a D-dimer test often can help rule out PE.
• Duplex ultrasound. This noninvasive test uses sound waves to create pictures of how blood flows through your veins. It's the standard test for diagnosing DVT. For the test, a technician gently moves a small hand-held device (transducer) on your skin over the body area being studied. Sometimes a series of ultrasounds are done over several days to determine whether a blood clot is growing or to check for a new one.
• Venography. A dye is injected into a large vein in your foot or ankle. An X-ray creates an image of the veins in your legs and feet, to look for clots. The test is invasive, so it's rarely performed. Other tests, such as ultrasound, often are done first.
• Magnetic resonance imaging (MRI) scan. This test may be done to diagnose DVT in veins of the abdomen.