The D-Dimer test measures protein fragments produced during the formation and breakdown of blood clots. When a clot forms, fibrin is generated to stabilize it and is subsequently degraded by fibrinolysis. D-Dimer is a specific byproduct of this process.

This test is used to assess the presence of abnormal clot formation and is particularly valuable in the diagnosis of thrombotic conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE), and disseminated intravascular coagulation (DIC).