Although D-dimer results within a typical range can rule out pulmonary embolism, high results alone can’t diagnose this condition. Doctors usually need to run extra tests to make a diagnosis.

A D-dimer assay measures the levels of a specific protein that remains in the blood after blood clots break down. It can help doctors diagnose blood clotting conditions, including pulmonary embolism.

However, an elevated D-dimer result may also indicate other blood clotting conditions.

Keep reading to learn about the D-dimer test in diagnosing pulmonary embolism, other tests a doctor may run, and what other conditions an elevated result can help diagnose.

The D-dimer test alone can’t diagnose a blood clotting condition like pulmonary embolism.

The D-dimer test detects the presence of the D-dimer protein in your blood. Your body makes this protein when a blood clot breaks up. Having a high amount of D-dimer in your blood may mean that you have a blood clotting condition like pulmonary embolism.

What’s considered a typical value of D-dimer protein in the blood can vary by lab. This may be due to differences in equipment or technique, among other factors.

According to some 2019 research, pulmonary embolism may cause a D-dimer test result above 500 nanograms per milliliter (ng/mL), and people with a result above 2,152 ng/mL were significantly more likely to have this condition.

However, a test result at 500 ng/mL or above doesn’t necessarily indicate pulmonary embolism or another clotting condition.

If your result is above the lab’s standard range, your doctor will likely order additional tests and imaging to find an explanation.

A D-dimer result above the typical range means that your blood contains more of the protein byproduct of clots breaking down. This may indicate a blood clotting condition.

Blood clotting conditions include:

  • pulmonary embolism, or a blood clot in the lungs
  • deep vein thrombosis, or a blood clot in one of the deep veins in the arms or legs
  • disseminated intravascular coagulation, which is a rare, life threatening situation that can happen due to excessive clot formation or when a clot is bleeding
  • stroke, or a blood clot that disrupts blood flow to the brain

Increased D-dimer levels can also result from:

If a doctor suspects that you may have pulmonary embolism, they’ll likely order additional tests. These tests can help doctors determine if and where you have blood clots as well as better understand your heart and lung function.

Blood tests can include:

  • arterial blood gas analysis
  • troponin blood test, which can indicate damage to the heart
  • B-type natriuretic peptide test, which can indicate that your heart is working too hard to pump blood

Imaging tests can include:

  • electrocardiography, which measures the heart’s electrical activity
  • chest radiograph, or chest X-ray
  • computed tomography pulmonary angiography, a CT scan that can identify blood clots in the lungs
  • ventilation-perfusion scan, which measures how well air and blood flow through the lungs
  • pulmonary angiography, a test that shows blood flow through the lungs
  • magnetic resonance angiography, a type of imaging test that lets doctors see blood vessels
  • echocardiography, which uses sound waves to produce images of the heart
  • compression ultrasonography, an ultrasound technique that checks for blood clots

Pulmonary embolism can cause symptoms, though not everyone experiences them. They may come on slowly over time or rapidly over the course of minutes.

If you think you may have symptoms of pulmonary embolism, seek emergency medical attention.

An elevated D-dimer test means that your blood has a higher amount of the D-dimer protein formed as a byproduct of blood clots breaking down.

A high amount of this protein can potentially indicate a blood clotting condition, such as pulmonary embolism, but it can also have other causes.

Because of this, doctors often need to run additional tests to diagnose the cause of the elevated test result.