AbstractD‐dimer is an indirect marker of fibrinolysis and fibrin turnover; this molecule exhibits unique properties as a biological marker of hemostatic abnormalities as well as an indicator of intravascular thrombosis. D‐dimer is a soluble fibrin degradation product that results from the systematic degradation of vascular thrombi through the fibrinolytic mechanism. Because of this, the D‐dimer serves as a valuable marker of activation of coagulation and fibrinolysis in a number of clinical scenarios. Most commonly, D‐dimer has been extensively investigated for excluding the diagnosis of venous thromboembolism (VTE) and is used routinely for this indication. In addition, D‐dimer has been evaluated for determining the optimal duration of anticoagulation in VTE patients, for diagnosing and monitoring disseminated intravascular coagulation, and for monitoring other conditions in which the patient is at high risk of bleeding or thrombosis. Limitations of the assay include D‐dimer elevation in a constellation of clinical scenarios (age, pregnancy, and cancer) and lack of clinical standardization.