Skip to main content

Warning notification:Warning

Unfortunately, you are using an outdated browser. Please, upgrade your browser to improve your experience with HSE. The list of supported browsers:

  1. Chrome
  2. Edge
  3. FireFox
  4. Opera
  5. Safari

Asthma diagnosis and tests

Your GP can often diagnose asthma from your symptoms and some tests.

What happens at your GP visit

Your GP may ask:

  • what symptoms you have
  • when symptoms happen and how often
  • if anything seems to trigger your symptoms
  • if you have conditions such as eczema or allergies, or a family history of them

They may ask you to do some breathing tests. This is to confirm if you have asthma.


Children under 5 often cannot do breathing tests properly. Your GP may offer treatment without doing a breathing test if your child is under 5 and has symptoms.

Your GP may refer you to an integrated care hub (care hub) if:

  • you need spirometry or other breathing tests
  • your asthma is difficult to control

Lung function tests

Your GP or care hub team may do tests to check how well your lungs work.


Spirometry is a test to diagnose and monitor certain lung conditions.

You blow into a device called a spirometer. A spirometer measures how much air you can breathe out in 1 forced breath.


Peak flow test

You blow into a device called a peak flow meter. A peak flow meter measures how fast you can breathe out. You may need to check your peak flow regularly to monitor your asthma.

Peak flow test

Other tests

Your GP or specialist may do other tests to confirm asthma or asthma triggers.

FeNO test

FeNO stands for fractional exhaled nitric oxide. You breathe into a device that measures the level of nitric oxide in your breath.

The level of nitric oxide can show:

  • how inflamed your airways are
  • if you have certain types of allergic asthma

Challenge test

You breathe in a powder or mist that can irritate your airways and make them get narrower. The test shows how sensitive your airways are.

This test is only done if other tests do not give a clear result. You do the test in a hospital.

Allergy tests

Your GP or care hub team may refer you for skin testing.

This is to see if you are allergic to common allergens that can trigger asthma, such as:

  • pollen
  • dust mites
  • flakes of skin or hair from animals
  • mould

Page last reviewed: 8 December 2023
Next review due: 8 December 2026

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 9.