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 when a blood clot breaks down.

A D-dimer test helps diagnose or rule out blood clotting conditions. Your doctor may refer you for this test if you have symptoms of a serious blood clot or a condition that affects blood clotting, such as:

• deep vein thrombosis (DVT) — a blood clot in a deep vein, usually in the legs
• pulmonary embolism (PE) — a blood clot in a blood vessel in the lungs
• disseminated intravascular coagulation (DIC) — a serious condition that causes abnormal blood clotting throughout the body
• blood clotting caused by a snake bite
• thrombosis with thrombocytopenia syndrome (TTS) — a rare blood clotting condition

This test may also be used to check how long blood thinners (anticoagulant medicines) are needed for people being treated for a blood clot.

A D-dimer blood test is usually performed in a hospital or emergency care department.

If your GP refers you for a D-dimer test, they will give you a referral and recommend a pathology collection centre near you. Sometimes, your doctor may collect a blood sample in their clinic.

No special preparation is needed for a D-dimer test.

However, if you are having other blood tests done at the same time, you may need to prepare. Check with your doctor or the pathology collection centre if there is anything you need to do before your blood test.

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

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

The D-dimer test is usually used together with other blood tests and imaging scans. This is because the D-dimer test alone cannot identify the location or cause of the blood clots.

Other reasons for a positive D-dimer test

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

• in older people
• during pregnancy
• if you smoke
• after surgery
• if you have an infection, inflammation or high levels of a protein in your blood found in people with rheumatoid arthritis
• if you have certain health conditions, such as liver disease or cancer

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. They can explain what they mean in your situation.

Pathology Tests Explained (Opens in new tab) has information about D-dimer testing (Opens in new tab).

Read our 'Guide to blood testing' to learn more about blood tests, including:

• what to consider before having the test
• what happens during a blood test
• how accurate results are
• blood test costs

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.