What is a D-dimer test?

A D-dimer test is a blood test that checks for blood-clotting problems.

This test measures the amount of D-dimer, a protein your body makes to break down blood clots.

Why would I need a D-dimer test?

Your doctor might ask you to have this test if you have symptoms of blood clotting problems.

A D-dimer test may be used as part of the assessment for different problems including:

• deep vein thrombosis (DVT) — a blood clot in your deep veins, usually in the legs
• pulmonary embolism — a blood clot in an artery in your lungs
• disseminated intravascular coagulation (DIC) — a condition that stops your blood from clotting normally
• blood clotting caused by a snake bite
• thrombosis with thrombocytopenia syndrome (TTS) — a very rare blood clotting condition

A D-dimer test is commonly used to rule out problems such as DVT.

If you are having treatment for DIC, your doctor may use the D-dimer test to monitor your condition.

How do I prepare for a D-dimer test?

No preparation is needed for this test. A blood sample is usually taken from a vein in your arm.

Understanding your results

A positive test means the D-dimer level in your body is higher than normal. It suggests you might have a blood clot or blood clotting problems.

A normal D-dimer level usually shows that a clotting problem is unlikely.

The D-dimer test is usually used with other blood tests and imaging scans. That’s because the D-dimer test cannot tell where in the body blood clots are or what may have caused them.

Sometimes the D-dimer test can be positive in people without clotting problems. This can happen in:

• older people
• during pregnancy
• if you are a smoker
• if you have recently had surgery

D-dimer tests can also be positive in people with other conditions, such as severe infections.

Anticoagulant medicines (used to prevent and treat blood clots) can also affect your D-dimer test results.

It’s important to discuss your results with your doctor, who can explain what the results mean in your situation.

Resources and support

Visit the Pathology Tests Explained website for more information about D-dimer testing.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.

Read this guide to blood testing to learn more about blood tests, including:

• what happens during a blood test
• the accuracy of your results
• the cost of your blood tests