Age-Adjusted D-Dimer Calculator
Calculate an age-based threshold in the correct assay units.
Choose the reporting type printed on your laboratory report.
Photos are illustrative; identify FEU or DDU from the report text.
Age & reporting units
Age-adjusted threshold
Age 60 years • FEU reporting
Threshold value only — no laboratory result has been assessed.
How the cutoff changes with age
How is this calculated?
1. Select the age rule
Age > 50 → cutoff = Age × 10
2. Substitute your age
60 × 10 = 600 ng/mL FEU
3. Convert the reporting unit
600 ÷ 1000 = 0.60 mg/L FEU
FEU and DDU are different reporting systems
Use the appropriate rule; confirm assay-specific laboratory guidance.
Calculation & assumptions
For FEU: use 500 ng/mL at age 50 or younger; use age × 10 above 50.
For DDU: conventional 250 ng/mL; age × 5 above 50. Adult use; assay-specific guidance takes priority.
Example: 60 years → 600 ng/mL FEU → 0.60 mg/L FEU
This tool calculates a threshold, not the probability of a blood clot.
Frequently asked questions
What does the Age-Adjusted D-Dimer calculate?
It calculates an age-based D-dimer cutoff in the selected FEU or DDU reporting system. It does not assess a measured laboratory result or calculate the probability of a clot.
Which values should I enter?
Enter adult age in completed years, select FEU or DDU exactly as printed on the laboratory report, and choose the output unit. Do not infer the reporting system from specimen tube color.
What formula does this calculator use?
For FEU at age 50 or younger, the conventional threshold is 500 ng/mL; above 50, age × 10 ng/mL. For DDU, the corresponding rules are 250 ng/mL and age × 5 ng/mL. Assay-specific laboratory guidance takes priority.
Why might my result differ from another source?
Check age, FEU versus DDU, concentration units, the assay-specific reference limit and the clinical diagnostic pathway. These are not interchangeable. A different laboratory may have a different validated cutoff.
Does the result update automatically?
Yes. Valid age, reporting-type and output-unit changes update the threshold, chart and worked solution immediately. Invalid inputs clear the estimate and disable exports.
More questions (7)
Can this result rule out pulmonary embolism?
No. This tool returns a cutoff only. ACEP supports age-adjusted D-dimer within selected adult suspected-PE pathways using a highly sensitive assay and clinician-assessed low or intermediate pretest probability. The threshold alone does not exclude PE.
What happens at age 50 or younger?
For adults 50 or younger, the conventional cutoff is used: 500 ng/mL FEU or 250 ng/mL DDU. Age adjustment begins above 50. At exactly 50, the two expressions give the same numerical threshold.
Are ng/mL and µg/L the same?
Yes: 1 ng/mL equals 1 µg/L. Divide by 1,000 to express the same concentration in mg/L. This concentration conversion does not change FEU into DDU.
Can FEU and DDU results simply be interchanged?
No. They are different reporting systems. Select the appropriate validated rule for the assay in use and confirm local laboratory guidance; this tool does not convert an individual measured FEU result into a DDU result.
What ages are accepted?
This adult calculator accepts whole-number ages from 18 to 120 years. The upper bound is a software limit. It does not extend the evidence to every patient or replace validation of the clinical pathway.
Does a tube color identify FEU or DDU?
No. The photographs are illustrative. Identify FEU or DDU from the report text and the laboratory assay information.
Does an elevated D-dimer prove a blood clot?
No. D-dimer can be elevated for several reasons. Diagnosis requires clinical assessment and an appropriate validated diagnostic pathway.
Sources & References
Adult suspected PE policyClinical policy on use of D-dimer in suspected pulmonary embolism.
ADJUST-PE studyRighini et al., 2014Age-adjusted D-dimer cutoff levels in suspected PE.
NG158 • D-dimer testingD-dimer testing in suspected venous thromboembolic diseases.References provide context, not endorsement. No institutional certification or review is claimed.
Page information
Updated: October 27, 2026