Breathing and lung function tests

Getting ready for your test

Breathing keeps us alive. It provides the oxygen that our bodies need and removes carbon dioxide, the waste gas that we produce. 

If you have problems with your breathing, your health care professional may suggest taking one or more tests. These can help to work out:

  • if your lungs are working normally, or if there is a problem
  • if there is a problem, what type of problem it is
  • if there is a problem, how severe is it

Highly-trained health care professionals will run your tests. They will make sure the equipment gives an accurate result and that it is hygienic to use, for example by using a separate, disposable mouthpiece for each person.


  • The results of tests can be used together with your medical history, symptoms and examination results as well as X-rays and scans to help guide your treatment.
  • Different people may need more or less complicated tests. Sometimes the tests need to be done only once to see what the problem is. Sometimes they are repeated to monitor changes over time or response to treatment.
  • When you get your results, ask your health care professional to explain them to you. Keep asking questions until you understand what your results mean.

Preparing for your test

When you’re going for a test, you may get a leaflet or an appointment letter with specific instructions. Read them carefully before your test. For some tests, you may be asked:

  • to wear loose-fitting clothing, or suitable shoes for a walking test
  • to stop smoking for 24 hours before the test (if you smoke, this can alter the results of some tests)
  • to avoid eating for some hours before
  • to avoid drinking alcohol and caffeinated drinks (like coffee, tea, cola or energy drinks) for some hours before
  • not to take your medication for some hours before
  • to bring along your medication, such as inhalers

If you’re unsure how to prepare, get in touch with the person who made the appointment for you.

If you’ve had a chest infection or a flare-up of symptoms and taken drugs such as steroids or antibiotics to treat it, this may affect your test results. If your test appointment is within 4–6 weeks of this, check with your health care professional about going ahead. Remember to tell whoever does your test about your recent chest infection and the drugs used to treat it.

Questions about your test

This information gives general information about breathing and other tests. But you may have more detailed questions. We’ve suggested some questions you could ask when your health care professional suggests you have some tests done or at the test appointment itself:

  • What is the test for?
  • Who will carry out the test, and where?
  • What will happen during the test and how long does it take?
  • Do I need to prepare for the test?
  • Will there be any side effects and how long will they last?
  • How and when will I get the results?

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

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Download this information (247KB, PDF)

Last medically reviewed: January 2017. Due for review: January 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.