D-Dimer
D-dimer is a small protein fragment left over when the body dissolves a fibrin clot. Its primary clinical use is to rule out venous thromboembolism (deep vein thrombosis, pulmonary embolism) in patients with a low or intermediate pre-test probability — a normal D-dimer in that setting safely excludes a clot without imaging. It is also elevated in disseminated intravascular coagulation (DIC) and after surgery or trauma.
Reference Ranges
Male
0 – 0.5
µg/mL FEU
Female
0 – 0.5
µg/mL FEU
Child
Consult pediatrician
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
A D-dimer below 0.5 µg/mL FEU, in a patient with a low or intermediate clinical probability of VTE, effectively rules out deep vein thrombosis and pulmonary embolism. No further imaging is usually needed.
What High Levels Mean
An elevated D-dimer is non-specific. Causes include venous thromboembolism, pregnancy, surgery, trauma, cancer, recent infection (including COVID-19), liver disease, and advanced age. A positive D-dimer always requires follow-up imaging (ultrasound, CT angiography) for definitive diagnosis.
Frequently Asked Questions
Why was my D-dimer high after COVID?
COVID-19 causes widespread endothelial and microvascular inflammation, which activates coagulation and leaves behind D-dimer fragments. Mild elevations for several weeks after recovery are common and usually clear on their own. A rising or very high D-dimer during active COVID is a warning sign that warrants clinical evaluation.
Should D-dimer be used to screen for blood clots?
No. D-dimer is a rule-out test, not a rule-in test. Because it is elevated in many non-clot conditions (pregnancy, infection, age, cancer), a positive result alone cannot diagnose a clot — it only triggers imaging. Using D-dimer as a screening test without clinical suspicion leads to unnecessary imaging and anxiety.
Does age affect D-dimer?
Yes. D-dimer rises steadily with age. Many labs now apply age-adjusted cutoffs (age × 10 µg/L for patients over 50) to reduce false positives. A D-dimer of 700 µg/L may be abnormal in a 30-year-old but normal in a 75-year-old with the age-adjusted cutoff.
Related Coagulation tests
See all →Prothrombin Time / INR (PT/INR)
Measures how long blood takes to clot via the extrinsic pathway.
INRCoagulationActivated Partial Thromboplastin Time (aPTT)
Measures clotting via the intrinsic pathway — used for heparin monitoring.
secondsCoagulationFibrinogen
Blood protein that forms the scaffold of a clot.
mg/dLThis information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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