How is asthma diagnosed?

Your health care professional makes a diagnosis of asthma based on your symptoms, family history of allergies and the results of breathing tests.

If you have asthma, your symptoms will tend to:

  • come and go over a period of time
  • be worse at night and in the early morning
  • be made worse when you come into contact with a trigger like smoke

Breathing tests help to confirm the diagnosis. People with asthma symptoms have narrowed airways so they breathe less air out. The amount of air you breathe out is measured by spirometry or by a peak flow meter, which you can use at home. 

Man breathing into a sophisticated spirometer

BLF Joan McCarthy peak flow test

Your health care professional may also do other breathing tests. For example, to measure inflammation of the lung lining or a chest X-ray to help to rule out other lung problems.

Next: Treatment for asthma >

If you have concerns or need advice, call our helpline on 03000 030 555 between 9am and 5pm on a weekday or email them.

We'll take good care of your personal info and you can update the way we contact you at any time - check out our privacy policy at to find out more.

Download our asthma PDF (380KB) Order your free asthma leaflet >

Last medically reviewed: April 2017. Due for review: April 2020

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.