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D-Dimer Unit Converter
D-Dimer is a protein fragment produced when the body breaks down a blood clot (fibrinolysis). It indicates that the coagulation and fibrinolytic systems have been activated. It is measured by immunoassay and is crucial in the workup for Venous Thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE).[Image of coagulation and fibrinolysis pathway]
Because of its high Negative Predictive Value (NPV), a normal D-Dimer result is effective for safely ruling out VTE in low-risk patients. However, levels rise significantly in many non-thrombotic conditions (cancer, pregnancy, trauma, surgery), limiting its diagnostic specificity. The major unit convention challenge is converting between the actual D-Dimer mass (DDU) and the Fibrinogen Equivalent Mass (FEU), which is approximately double the DDU value (1DDU ≈ 2FEU).
SI Units (Mass / DDU)
RecommendedDDU is the true mass of the D-dimer fragment.
Conventional Units (FEU / mg/L)
Clinical Context
Cut-off Threshold: The general exclusion threshold for VTE is < 500 ng/mL FEU or < 250 ng/mL DDU. Modern guidelines (PERC Rule, Wells Score) often use age-adjusted cut-offs (e.g., age x 10ng/mL) in older patients.
The key conversion challenge is the 1DDU : 2FEU ratio. Always confirm which units your laboratory reports to apply the correct clinical threshold. Falsely positive results are common in the hospital setting due to inflammation.
Clinical References
How to Use This Calculator
Follow these steps to get accurate clinical conversions instantly.
Enter Values
Input the value you have into the correct unit field (e.g., ng/mL (FEU)). This determines the calculation base.
Automatic Conversion
The calculator works in real-time. Conversions between DDU and FEU are calculated instantly based on the 1:2 ratio.
Verify Units
Be sure you use the appropriate cut-off for the unit shown (e.g., 500 ng/mL (FEU);250 ng/mL (DDU)).
Reset
Use the Clear button to reset all fields before starting a new calculation.
Frequently Asked Questions & Tips
FEU (Fibrinogen Equivalent Units) reports the value as if it were intact fibrinogen, which has roughly twice the mass of the measured D-Dimer fragment (DDU). Most US labs use FEU.
D-Dimer is typically measured in $\text{ng}$ or $\mu\text{g}$ per volume. $\text{mg/dL}$ would result in very small decimal values, which is undesirable in clinical reports.