D-Dimer
Also written as: D-di, fibrin degradation fragment
A fragment left over when blood clots dissolve, used mainly to help rule clots out.
What it measures
The level of D-dimer, a small protein fragment released when the body breaks down a blood clot. Its presence shows that clot formation and breakdown have been happening somewhere in the body.
Why a doctor orders it
Most often ordered when a clot in a leg vein (deep vein thrombosis) or in the lungs (pulmonary embolism) is being considered. Its main strength is in ruling clots out, because a low value makes a significant clot unlikely.
What is generally associated with a higher result
Broadly associated with any recent clotting activity, but the test is famously nonspecific. Infection, inflammation, surgery, injury, cancer, pregnancy, and simply getting older all raise it without any dangerous clot being present. A raised value usually leads to imaging rather than standing as an answer on its own.
What is generally associated with a lower result
Broadly associated with an absence of significant recent clot formation and breakdown. Low values are generally not pursued.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Older age - levels rise steadily with age
- Pregnancy, which raises it progressively as it advances
- Recent surgery, injury, or dental work
- Any recent infection or inflammation
- Smoking
Questions to take to your appointment
- Could my age, a recent illness, or pregnancy account for the level seen?
- Would imaging, such as an ultrasound or CT scan, be the next step?
- Was an age-adjusted approach used when reading this result?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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