D-dimer — Normal Range & Interpretation

Clinical Context

D-dimer measures a fibrin degradation product released when the body breaks down a clot. The test reflects active coagulation and fibrinolysis, making it a sensitive screening tool for thromboembolic disease. Clinicians use it to rule out venous thromboembolism in patients with low to moderate pretest probability, since a negative result effectively excludes clot formation.

Elevations occur with deep vein thrombosis, pulmonary embolism, and disseminated intravascular coagulation. Non-thrombotic causes also raise D-dimer, including pregnancy, advanced age, malignancy, recent surgery, trauma, infection, sepsis, liver disease, and inflammatory conditions. This broad differential gives D-dimer high sensitivity but poor specificity, so a positive result requires confirmatory imaging such as duplex ultrasound or CT pulmonary angiography. D-dimer holds little value in high-risk patients, who proceed directly to imaging regardless of the result.

FNPs see D-dimer on the boards most often in the context of VTE workup. Expect questions that pair a patient with Wells criteria and ask for the next step, where a low-probability score combined with a negative D-dimer rules out PE or DVT. Questions also highlight the high sensitivity and low specificity of the test, age-adjusted cutoffs in older adults, and the appropriate use of D-dimer in DIC alongside thrombocytopenia, prolonged PT/PTT, and low fibrinogen.

Related Labs

• PT — seconds
• INR
• aPTT — seconds

Sources

• MedlinePlus
• ARUP Consult