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D-dimer
A fibrin breakdown product — a marker that a clot has formed and dissolved. A negative result helps rule out thrombosis.
Other names: D-dimer, Fragment D-dimer, Fibrin degradation fragmentSection: Blood clotting
Updated: August 31, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortD-dimer is a fibrin breakdown product marking clot formation and dissolution. A low (negative) result at low clinical probability helps the doctor rule out thrombosis without imaging; a high result needs further workup but is not a diagnosis by itself.
Reference ranges
Group
Reference range
Typical result in a healthy person
low or within the lab reference (negative)
The source describes interpretation qualitatively: a low or normal level makes thrombosis unlikely; a high level requires further testing. Cut-offs depend on the assay (mg/L FEU or DDU) and are printed on your lab report. Reference ranges vary between laboratories and assays — use the range printed on your own lab report.
Check your value
Enter your result — we will show how it compares with a typical range. Match the units of the selected row.
Approximate comparison with a typical range, not a diagnosis. Reference intervals vary by laboratory and method — check your report; result interpretation is done by a doctor.
What this marker is
D-dimer is a fragment released when fibrin — the mesh of a blood clot — is broken down. When a clot forms in a vessel, the fibrinolytic system gradually dissolves it, and fragments including D-dimer appear in the blood.
The test's main value is a negative result: a normal D-dimer at low clinical probability lets the doctor effectively rule out deep vein thrombosis or pulmonary embolism without imaging. A raised result is non-specific — it grows with inflammation, after surgery, in pregnancy and with age — so it never makes the diagnosis alone: ultrasound or CT angiography is required.
When it is high
Deep vein thrombosis and PEThe main reason the test is ordered. An elevation must be confirmed by imaging.
Postoperative period and traumaActive clotting and tissue repair predictably raise D-dimer.
PregnancyA physiological rise by trimester — interpretation only on special scales by the doctor.
Inflammation, infections, cancerAny activation of the clotting system raises the level — a positive result does not equal thrombosis.
Older ageIn people over 80, D-dimer is often moderately raised without thrombosis; age-adjusted cut-offs apply.
When it is low
Normal findingA low level is the expected result in a healthy person and the strongest argument against a fresh thrombosis.
Anticoagulant therapyTreatment can cause a false-negative result — the doctor accounts for it.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
Recent surgery and traumaPregnancyInflammation and infectionsAnticoagulants (false negative)Age over 80
How to prepare
Blood from a vein; no special preparation needed. Tell your doctor about anticoagulants (possible false negatives), pregnancy, recent surgery and injuries — all of this changes interpretation.
When a retest makes sense
Not tracked routinely over time — the test answers a one-off rule-out question; repeat only as the doctor advises.
Who usually reviews this result
A result outside the reference range is usually reviewed by: GP or phlebologist; for suspected pulmonary embolism — emergency care. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: D-dimerFragment D-dimerFibrin degradation fragmentFibrin split products
Units
Measured in: mg/L FEU or DDU (assay-dependent)
mg/L=ng/mL
ng/mL = mg/L × 1000. The cutoff depends on the assay: ~500 ng/mL for FEU, ~230 for DDU.
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
No. The test is very sensitive but not specific: the level rises with inflammation, after surgery, in pregnancy and with age. A high D-dimer is a reason for vein ultrasound or CT, not a diagnosis.
Why take the test at all?
For the negative result: at low probability of thrombosis, a normal D-dimer lets the doctor skip expensive imaging.
What units is D-dimer measured in?
Usually mg/L FEU or DDU, with cut-offs differing roughly twofold between assays — compare your result only with your own lab's reference.
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