D-Dimer Test

This test measures the amount of D dimer in your blood. D dimer is a protein fragment that is formed when your body breaks down (dissolves) blood clots. Blood clots normally form to help control bleeding when a blood vessel is injured. Your body normally limits blood clot formation. However, some conditions disrupt your body's ability to limit blood clot formation, leading to abnormal or excessive clotting and high levels of D dimer in your blood. This abnormal or excessive clotting can cause the formation of blood clots along the inside walls of your blood vessels (thrombosis). A blood clot formed by thrombosis (thrombus) can block blood vessels and damage organs and body tissues.

The D-dimer test is used to help diagnose conditions that cause abnormal or excessive blood clotting. This test may also be used to monitor people who are being treated for disseminated intravascular coagulation (decreasing amounts of D dimer means the treatment is working).


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results. Contact your health care provider to discuss any questions you have about your results.

Range of Normal Values

Ranges for normal values may vary among different labs and hospitals. You should always check with your health care provider after having lab work or other tests done to discuss whether your values are considered within normal limits. The range of normal values is listed as follows:

  • Quantitative test: less than 250 ng/mL D-dimer units or less than 0.5 µg/mL fibrinogen equivalent units.  

  • Qualitative test: negative.

A normal test result usually means that you do not have a condition that causes abnormal or excessive blood clotting. However, elevated levels of fat in your blood (lipemia) can cause D-dimer test results to appear negative when they are positive (false-negative result). Additionally, antibodies in people with rheumatoid arthritis can cause D-dimer test results to appear positive when they are negative (false-positive result).

Meaning of Results Outside Normal Value Ranges

An increased quantitative D-dimer test result or positive qualitative D-dimer test result is abnormal. An abnormal result may mean that you have one of the following serious clotting conditions:

  • Deep vein thrombosis.

  • Pulmonary embolism.

  • Disseminated intravascular coagulation.

Your health care provider will ask about your medical history and risk factors for thrombosis and may order additional blood tests or imaging exams because abnormal D-dimer test results are also seen in a number of other conditions that cause increased clotting, such as:

  • Recent surgery.

  • Traumatic injuries.

  • Infection.

  • Certain cancers.

  • Pregnancy.

  • Liver disease.