Definition

D-dimer is a protein fragment that appears when a clot dissolves in the body. Its level in the blood shows whether clot formation or breakdown is ongoing.

Purpose

Used in screening for clotting disorders: deep vein thrombosis (DVT), pulmonary embolism (PE), disseminated intravascular coagulation (DIC) and stroke risk assessment.

Results

  • Low/normal, you probably do not have a clotting disorder. This is where the test's real strength lies: a negative result is valuable for ruling out a clot.
  • High, may point to a clotting disorder, but additional testing is needed for a definitive diagnosis.

Normal Values

Laboratory-specific, refer to the reference range on your report.

Risks and Limitations

False positives are very common. Many conditions other than a clot raise D-dimer: pregnancy, heart disease, rheumatoid arthritis, recent surgery, advanced age and immobility. In addition, blood-thinning medications can cause a false negative result.

Related Tests

PT / INR (Prothrombin Time)

The PT test measures how many seconds it takes for a clot to form in a blood sample. The INR is a standardized ratio that makes this result comparable between different

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aPTT (Activated Partial Thromboplastin Time)

Measures the number of seconds it takes for blood to clot. Unlike PT, it evaluates a different subset of clotting factors and their function.

Go to term →

Other related tests not yet in the glossary: Doppler ultrasound, CT angiography, V/Q scan (to locate the clot).