If your doctor thinks that you have DVT, you probably will have an ultrasound test to measure the blood flow through your veins and help find any clots that might be blocking the flow. You might have two or three more ultrasounds over the next 2 weeks.

To see if you need an ultrasound, the doctor will do a physical exam. This will include checking your heart and lungs and checking your legs for warmth, swelling, bulging veins, or changes in skin color. Your doctor will also ask questions about your past and current health. These questions may include:

• Do you have any swelling or pain in your legs?
• Have you had a blood clot before?
• What medicines do you take?
• Have you had surgery recently, or have you been on any long trips lately?

Other tests

More tests may be used when ultrasound results are unclear. These tests often aren't needed, but they may help diagnose or exclude a blood clot in the leg. These tests may include:

• D-dimer test.
• MRI.
• CT scan.

If your doctor thinks you might have a pulmonary embolism, he or she may test your lungs.

Blood thinner testing

If you are treated with anticoagulant medicines, you may need periodic blood tests to monitor the effects of the anticoagulant on the blood. Blood tests include:

• Activated partial thromboplastin time (APTT) to monitor treatment with heparin.
• Prothrombin time (PT), also referred to as INR, to monitor treatment with warfarin (Coumadin).

Tests for clotting problems

Testing might be done if you have or had one or more of the following problems.

• A blood clot in a vein that has no clear cause
• A blood clot at age 45 or younger
• A blood clot in a vein at an unusual location, such as the gastrointestinal region, the brain, or the arms
• A first-degree family member (mother, father, brother, or sister) who had a blood clot in a vein before age 45 or had problems with blood clotting

Screening for these problems in the general population isn't routinely done.