D-Dimer

Does this test have other names?

Fragment D-dimer, fibrin degradation fragment

What is this test?

This is a blood test to look for a substance called D-dimer. This test is used to rule out a blood clot.

D-dimer is a protein fragment from the break down of a blood clot. Blood clots generally begin to slowly break down after they are formed, and this process releases D-dimer into the blood. 

Why do I need this test?

You may need this test if your healthcare provider suspects you have a dangerous blood clot. A blood clot that forms in a deep vein is called a deep vein thrombosis (DVT). A DVT is most commonly found in the legs. If the clot travels to the lungs, it's called a pulmonary embolism (PE). In the lungs, the clot can cut off the flow of blood. This is a medical emergency and may cause death.

Symptoms of a blood clot include:

• Leg swelling (edema)

• Leg pain or tenderness

• Leg redness

If you have these symptoms, call your healthcare provider.

You may also have a D-dimer test if you have symptoms of a blood clot in the lungs, such as:

• Trouble breathing

• Coughing (may cough up blood)

• Fast heartbeat

• Chest pain 

• Sweating

• Fainting

If you have these symptoms, call 911 or get emergency help.

People with blood clots often have 1 or more risk factors. These risk factors include:

• Major surgery (for example, hip surgery) or injury (for example, a broken leg)

• Not being able to move for long periods of time (for example, from being in the hospital, or taking long trips by plane or car)

• Pregnancy or recent childbirth

• Certain cancers

• Antiphospholipid syndrome

• Inherited clotting disorder, such as factor V Leiden mutation

You may also need this test to help diagnose and monitor treatment for other conditions.

What other tests might I have along with this test?

You may need more blood tests, including platelet count, fibrinogen, and prothrombin time. 

If your D-dimer test is positive, you will have other tests. You may have the following imaging tests to look for blood clots:

• Ultrasonography

• Computed tomography (CT) angiography

• Pulmonary angiography

• Ventilation/perfusion scanning 

These tests help your healthcare provider diagnose blood clots in your legs, arms, lungs, or other parts of the body.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.

An elevated D-dimer level is not normal. It is usually found after a clot has formed and is in the process of breaking down. If you are having significant formation and breakdown of blood clot in your body, your D-dimer may be elevated.

A negative D-dimer test means that a blood clot is highly unlikely.

A positive D-dimer test doesn't mean that you have a clot. There may be other reasons it is positive. More testing is usually needed.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore. 

What might affect my test results?

Levels may be higher in people with other problems. They include infection, heart attack (myocardial infarction), liver disease, cancer, and injury.

How do I get ready for this test?

You don't need to prepare for this test.