D-dimer (Blood Clot Test)
Also known as: D-dimer test, Clot test, D dimer test, D dimer zyada hona
D-dimer is a fragment released when a blood clot breaks down. It rises when the body is forming and dissolving clots.
Why it's ordered
Mainly to help rule out a blood clot in the leg (deep vein thrombosis) or lung (pulmonary embolism) when a doctor thinks the chance is low, and in some bleeding and clotting disorders.
Preparation
No preparation needed. Sudden breathlessness, chest pain or coughing blood is an emergency: go to hospital or call 1122.
Typical adult values
| Normal | below the lab's cut-off, often about 0.5 µg/mL FEU (500 ng/mL); units and cut-offs differ between tests |
|---|
Ranges vary between labs and methods. Always use the range printed on your report.
If it's high
A raised D-dimer does not prove a clot. It is also high after surgery or injury, in pregnancy, infection (including COVID-19), cancer, liver disease and in older age. Your doctor decides whether a scan is needed.
If it's low
A normal D-dimer, when the doctor judges the chance of a clot to be low, makes a clot very unlikely.
Good to know
Because D-dimer rises naturally with age, some doctors use an age-adjusted cut-off for people over 50. A swollen, painful leg or sudden breathlessness needs prompt medical assessment whatever the D-dimer result.
Common questions
Does a high D-dimer mean I have a blood clot?
No. It is also high after surgery or injury, in pregnancy, infection, cancer, liver disease and in older age. Your doctor decides whether a scan is needed.
What is a normal D-dimer?
Below the lab's cut-off, often about 0.5 µg/mL FEU (500 ng/mL). Always use the range printed on your report.
Can a normal D-dimer rule out a clot?
Yes, when the doctor judges the chance of a clot to be low, a normal D-dimer makes a clot very unlikely.
When is it an emergency?
Sudden breathlessness, chest pain or coughing blood: go to hospital or call 1122.