First checks

When you first see the doctor, he or she will do a physical exam and ask questions about your medical history. These help your doctor decide what tests you need based on your risk for deep vein thrombosis (DVT).

Physical exam

Your doctor will check:

• Your heart and lungs.
• Your legs for warmth, swelling, bulging veins, or changes in skin color.

Medical history

Your doctor may ask:

• 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?

Ultrasound test

Ultrasound is the main test used to help diagnose DVT. It creates a picture of the flow of blood through the veins.

If your doctor thinks you should have more tests, you might have two or three more ultrasounds over the next 7 to 10 days.

Additional 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.
• Venogram.

If your doctor thinks you might have a pulmonary embolism, he or she may test your lungs. For more information, see the topic Pulmonary Embolism.

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

Special blood tests may help identify inherited blood-clotting problems that can increase your risk of forming blood clots or help explain why you got a blood clot. These tests check for genetic conditions or specific proteins in your blood.

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

• 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 has had a blood clot in a vein before age 45 or has had problems with blood clotting

Screening for these problems in the general population is not routinely done.