D-Dimer Blood Test Overview
A D-dimer test is a blood test that can be used to help rule out the presence of a serious blood clot.
When you get a cut or wound, your body starts a process called hemostasis to form a clot and stop you from losing too much blood. It forms threads of a protein called fibrin to keep the clot in place. Once you've healed, the clot breaks down into fragments. One of those fragments is called D-dimer. It’s part of a protein. Normally, with a little time, it goes away. But you can get high levels of D-dimer in your blood if you have a major clot like with deep vein thrombosis (DVT). This is a clot deep in one of your veins, usually in your legs, and it can lead to serious problems.
You may also hear this test called:
- Fragment D-dimer test
- Fibrin degradation fragment test
When Do I Need This Test?
The D-dimer test is most useful when your doctor wants to quickly rule out these causes:
DVT, which may give you swelling, pain, or redness in your leg.
Pulmonary embolism, or PE, a blood clot that has traveled to your lungs that may lead to:
- Trouble breathing
- Fast heartbeat
- Chest pain
Stroke, when blood flow to the brain is blocked or a blood vessel in the brain bursts. This causes brain cell death within minutes. You may:
- Have weakness or numbness in the face, arms, or legs, especially on one side of the body
- Be confused, dizzy, or uncoordinated
- Find it hard to speak or understand when someone speaks to you
Disseminated intravascular coagulation (DIC), a rare disorder in which the proteins that cause clotting become overactive. Many small clots may form throughout your blood vessels, blocking the blood flow that brings oxygen and nutrients to your brain and body. Symptoms include:
- Bleeding at wound sites or from your nose, gums, or mouth
- Blood in your stool or urine
- Chest pain
- Pain, redness, warmth, or swelling in your legs
A D-dimer test may also be used to check on your treatment for DIC. If D-dimer levels drop, it’s a sign that the treatment is working.
What Happens During the Test?
A D-dimer test usually takes just a few minutes. You can sit or lie down while a care provider finds the vein they wish to use and sterilizes the skin over it. They'll use a thin needle to take a small amount of blood in a test tube. Then they'll bandage the area.
Your blood sample will be taken to the lab for testing. Your doctor will share your results with you and explain what they mean.
How do I prepare for this test?
You don’t need to do anything special to get ready for a D-dimer test. You can eat or drink as you usually do before you have it.
Are there any risks that come with having this test?
You’ll feel a pinch or a sting when the needle goes in. The risks from a blood draw test are minor. But rarely, you could have:
- Multiple needle sticks from your provider looking for a vein
- Heavy bleeding
- Dizziness or fainting
- A bruise from blood collecting under the skin (hematoma)
What Do D-Dimer Results Mean?
What is a D-dimer normal range?
Different labs may do the test differently, so what’s considered normal or high can vary. Your doctor can help you understand more clearly what your results mean.
What does a low D-dimer level mean?
If your result comes back as low, negative, or normal, your blood has low levels of D-dimer and it's not likely that you have a clotting disorder.
What does a high D-dimer level mean?
If your result is high or positive, it means there are high levels of D-dimer protein in your blood. Your doctor will need to do more tests and imaging to see whether you have a blood clot, where it is, and what's causing it.
How long does it take to get the results of a D-dimer test?
Many times, your doctor will order a D-dimer test when you're in the emergency room. Results will come back within hours.
If your doctor is using the results of your test to track how well your treatment for DIC is working, you'll get the results within a couple of business days.
What Things Can Affect D-Dimer Test Results?
If you have a high likelihood of a clot or a clotting disorder, this test may not help your doctor make a diagnosis. Certain conditions can raise your chances of having a clot:
- Antiphospholipid syndrome, a disease in your immune system
- Clotting diseases that you’re born with
- Major surgery, such as a knee replacement
- Major injury, such as a broken leg
- Long periods of sitting or lying down, such as a long plane ride or hospital stay
- Pregnancy or if you recently had a baby
- Some cancers
If your doctor knows that your odds of having a clot are higher, they may skip the D-dimer in favor of other imaging tests to make a diagnosis.
Can medications or medical conditions affect D-dimer test results?
It's possible to have a high D-dimer level and not have a blood clot. An elevated result can also be due to:
- Older age (more than 80 years old)
- Sepsis (extreme reaction by the body to infection)
- Liver disease
- Some cancers
- Heart disease
- High lipid or triglyceride levels
- Recent injury or surgery
- An autoimmune disorder
- Rheumatoid arthritis
Certain medications that impact how your blood clots can affect your D-dimer results. They'll usually cause a false negative.
- Antiplatelet drugs such as aspirin, clopidogrel (Plavix), prasugrel (Effient), or ticagrelor (Brilinta)
- Statins, taken for high cholesterol
- The D-dimer test is a simple blood test that measures the levels of D-dimer protein, which is released when clots dissolve in the body.
- It's usually done as part of an emergency care situation to rule out a clot disorder such as pulmonary embolism (PE) or deep vein thrombosis (DVT). A negative or low result means that a clotting condition is possible, but highly unlikely.
- There's no standard measurement scale for this test, so your doctor will explain what your readings mean for the specific test you've taken.
What is a D-dimer normal range?
There are several types of D-dimer tests, so there isn't a standard range for a "normal" result. Your doctor will help you understand what the results from your particular test mean and what your next steps should be, if any.
What does an elevated D-dimer mean?
High levels of D-dimer protein in your blood mean that you may have a blood clotting condition. Certain other conditions or medications can also cause higher than normal D-dimer levels in the blood. Your doctor will need to do further tests to find out what condition you have and where the clot or clots may be in your body. They'll also need to rule out other things that can cause the test to give a false positive result.
If your doctor has ordered a D-dimer test to track your treatment for DIC, it may mean that your treatment isn't working well.
Can I control my D-dimer levels naturally?
There aren't any natural remedies proven to thin clots, but you can lower your chances of getting a clot by:
- Knowing your family history and risk factors
- Staying active
- Maintaining a healthy weight
- Taking a break to walk and stretch whenever you're sitting for long periods
- Not smoking