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

Diagnosing asthma

Asthma can usually be diagnosed from your symptoms and some simple tests.

Your GP will probably be able to diagnose it. But they may refer you to a specialist if you need other tests.

What to expect at your GP visit

Your GP may ask:

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

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

Young children

It's not always easy to do asthma tests for young children. Your GP might give your child an asthma inhaler. This is to see if it helps relieve their symptoms. This is usually until they're old enough to have the tests.

Tests for asthma

The main tests used to help diagnose asthma are:

  • FENO test
  • spirometry
  • peak flow test

FENO test

You breathe into a machine that measures the level of nitric oxide in your breath. This is a sign of inflammation in your lungs.


You blow into a machine that measures how fast you can breathe out. It also measures how much air you can hold in your lungs.

Read more about spirometry

Peak flow test

You blow into a handheld device. This measures how fast you can breathe out. This may be done several times over a few weeks to see if it changes over time.

Read more about the peak flow test

Page last reviewed: 9 December 2020
Next review due: 10 December 2023

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