Diagnosing pulmonary embolism 

It can sometimes be difficult to diagnose a pulmonary embolism because the symptoms vary between individuals and are similar to many other conditions.

Around half of all people who develop a pulmonary embolism do so while they're in hospital. 

The condition may be suspected if:

It's important that pulmonary embolisms are diagnosed correctly because treating them isn't always easy and the treatments used can cause side effects.


A number of tests may be used to help determine if you have a pulmonary embolism or to rule out other causes of your symptoms.

For example, you may have a chest X-ray or tests to check how well your lungs are working. You may also have some of the more specialised tests discussed below.

Blood tests

Blood tests can be carried out to detect a number of signs of pulmonary embolism. One of the main tests looks for a substance called D-dimer.

D-dimer is a protein found in the blood after a blood clot has broken down. A D-dimer test can be used to help diagnose blood clotting abnormalities such as thrombosis (where a blood clot develops in a blood vessel).

If your blood test result indicates high levels of D-dimer, it suggests that pieces of blood clot are loose in your bloodstream and may have become lodged in your pulmonary artery.

Computerised tomography pulmonary angiography

Computerised tomography pulmonary angiography (CTPA) is a procedure where you're injected with a special dye before having a computerised tomography (CT) scan. The dye makes it easier to see the blood vessels in your lungs during the scan.

A CT scan involves taking a series of X-rays to create a highly detailed image of the inside of your body. If there's a pulmonary embolism in one of your lungs, it may show up on the scan as a gap in your blood supply.

Ventilation-perfusion scan

A ventilation and perfusion scan is used to examine the flow of air and blood in your lungs.

Before having the scan, you'll be asked to inhale a tasteless, odourless and slightly radioactive gas through a mouthpiece. The gas helps highlight the air flow in your lungs during the scan.

You'll also be given an injection that contains a small amount of radioactive material to highlight the blood vessels in your lungs during the scan.

If the scan shows parts of your lungs have air in them but no blood supply, it may be the result of a pulmonary embolism.

Page last reviewed: 13/07/2015

Next review due: 13/07/2017