What a High D-Dimer Result Means

D-dimer is a protein fragment made when a blood clot dissolves in the body, and it is not usually found in blood unless the body is making or breaking up clots (National Library of Medicine (MedlinePlus), 2024-04-11). So the test measures clot turnover, not a clot itself.

It is a blood sample taken from a vein in your arm, and no special preparation is needed, so fasting and time of day are not part of it (National Library of Medicine (MedlinePlus), 2024-04-11 and 2026-02-27). The number reflects what is happening around the time of the draw, which is why it is often repeated if your situation changes.

Doctors order it to check whether you may have a blood clot and whether more testing is needed, including for deep vein thrombosis (a clot in a deep vein, usually in the leg), pulmonary embolism (a clot in the lung arteries), disseminated intravascular coagulation, or stroke (National Library of Medicine (MedlinePlus), 2024-04-11). It may also be used to monitor how well treatment for disseminated intravascular coagulation is working. Typical triggers for ordering it are leg swelling, pain or warmth in a limb, sharp chest pain, trouble breathing, coughing up blood, or a fast heartbeat (National Library of Medicine (MedlinePlus), 2026-02-27).

Its strength is in the negative. The American College of Physicians advised in 2015 that a high-sensitivity D-dimer be the first diagnostic test in patients with an intermediate pretest probability of pulmonary embolism, or in low-probability patients who do not meet all Pulmonary Embolism Rule-Out Criteria, and that neither D-dimer nor imaging be obtained in low-probability patients who meet all those criteria. A positive result means you may be making clots, but it does not say where they are or why (National Library of Medicine (MedlinePlus), 2026-02-27).

Ranges and units vary by laboratory and method. Some labs report in mcg/mL FEU, others in ng/mL, and some apply different cutoffs by age or clinical situation; one study reported pulmonary embolism being considered ruled out in outpatients with a low clinical pretest probability and a D-dimer below 1000 ng per milliliter (New England Journal of Medicine, 2019), which is a single study finding and not a universal rule. Use the range printed on your own report, not this table.

Ordered roughly from the most routine explanations to the less common ones.

• Older age - pushes it up. D-dimer rises with age in healthy people; in one population-based cohort the upper 95th percentile was 2.5 times greater in people over 70 than in people under 50 (International Journal of Laboratory Hematology, 2017), and being over 80 years old alone can make the test positive (National Library of Medicine (MedlinePlus), 2026-02-27).
• Recent surgery or trauma - pushes it up, because tissue healing involves clot formation and breakdown (National Library of Medicine (MedlinePlus), 2026-02-27).
• Pregnancy - pushes it up, with no clot necessarily present (National Library of Medicine (MedlinePlus), 2024-04-11).
• Infection and inflammation - push it up; general medical sources list infection and inflammatory conditions such as rheumatoid arthritis among the common non-clot causes (Labcorp, undated; Haematologica, undated).
• Immobility, heart disease, liver disease, or high blood lipid or triglyceride levels - push it up (National Library of Medicine (MedlinePlus), 2024-04-11 and 2026-02-27).
• Blood thinner medicines - can push the result down and cause a false negative (National Library of Medicine (MedlinePlus), 2024-04-11). Tell your clinician what you take; do not change anything on your own.
• Less common: an actual clot, such as deep vein thrombosis or pulmonary embolism, which is what the test is screening for and why a positive result is followed up rather than ignored (National Library of Medicine (MedlinePlus), 2024-04-11).
• Less common: cancer or disseminated intravascular coagulation, both of which are associated with raised D-dimer (Labcorp, undated).

1. Read the result next to your own lab's range. Find the cutoff and units printed on your report, since labs differ. A positive result means more information is needed, not that a clot has been found.
2. Expect your clinician to put it against your clinical picture. D-dimer is interpreted with pretest probability - your symptoms, risk factors, and recent surgery, pregnancy or illness - rather than alone (American College of Physicians, 2015).
3. Expect confirmatory or repeat testing if the result is high. That may mean imaging of the leg veins or chest, other blood tests, or a repeat D-dimer if your situation has changed since the draw. D-dimer is also sometimes repeated to monitor treatment for disseminated intravascular coagulation (National Library of Medicine (MedlinePlus), 2024-04-11).
4. Bring the printed report to the follow-up appointment. Take the lab slip, portal printout or after-visit summary with the number, units and date rather than relying on memory, and bring a current list of everything you take.
5. Know what should not wait. Sharp chest pain, sudden trouble breathing, coughing up blood or a fast heartbeat need immediate medical attention; new leg swelling, pain or warmth means calling your provider the same day rather than waiting (National Library of Medicine (MedlinePlus), 2024-04-11 and 2026-02-27). With no new symptoms and a scheduled appointment, it is reasonable to keep it.
6. Agree on an endpoint. Ask whether the result is now explained, whether anything needs rechecking, and when.