Pulmonary embolism

How is a pulmonary embolism diagnosed?

It can be hard for doctors to decide if you have a pulmonary embolism because the symptoms are similar to many other conditions. It’s important to diagnose it because treating a pulmonary embolism isn’t always easy and treatments can cause side effects.

If your doctor suspects a pulmonary embolism, you’ll have a number of tests,  such as a chest X-ray or an ultrasound scan to see if you have a blood clot in your leg, and tests to check how well your lungs are working.

Based on your doctor’s assessment, you may also have specialised tests such as:

  • a blood test to look for a protein called D-dimer. High levels of D-dimer in your blood suggest that pieces of blood clot are loose in your bloodstream.
  • a computerised tomography pulmonary angiography (CTPA) to see the blood vessels in your lungs. You are injected with a dye that helps to show your blood vessels and a scanner uses X-rays to build a detailed picture of the blood flow in your lungs.
  • a ventilation-perfusion scan, also called a V/Q scan or isotope lung scanning, to examine the flow of air and blood in your lungs. If the scan shows parts of your lungs have air in them but no blood supply, this may be the result of a pulmonary embolism. You will be asked to inhale a slightly radioactive gas and given an injection of slightly radioactive material. The radioactivity in this test is harmless to adults. But women who are, or might be, pregnant should tell the radiographer.
  • leg vein ultrasound to confirm you have a clot in the leg. This is not necessary if you’ve been diagnosed with clots by one of the other methods.​

Next: Treatment for pulmonary embolism >

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Last medically reviewed: March 2018. Due for review: March 2021

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.