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Spirometry (Lung Function Test)
Spirometry is a breathing test that measures how much air you can breathe out and how fast. It helps diagnose and monitor lung conditions such as asthma and COPD.
Quick answer
Spirometry (Lung Function Test): what it is and what the results mean
Spirometry measures lung function by recording the amount and speed of air you can blow out. It is a key test for diagnosing and monitoring conditions that affect breathing.
- Why it is done: It is used to diagnose and monitor asthma, COPD and other lung conditions, to assess breathlessness, and sometimes to check lung health before surgery or certain treatments.
- Understanding results: The results show whether airflow is reduced and in what pattern — for example an "obstructive" pattern in asthma or COPD.
What it is
Spirometry measures lung function by recording the amount and speed of air you can blow out. It is a key test for diagnosing and monitoring conditions that affect breathing.
Why it is done
It is used to diagnose and monitor asthma, COPD and other lung conditions, to assess breathlessness, and sometimes to check lung health before surgery or certain treatments.
What to expect
You take a deep breath and blow out as hard and long as you can into a mouthpiece, usually a few times. Sometimes the test is repeated after an inhaler to see if breathing improves. It takes around 15–30 minutes.
Understanding the results
The results show whether airflow is reduced and in what pattern — for example an "obstructive" pattern in asthma or COPD. They are interpreted alongside your symptoms, history and response to inhalers.
Good to know
Risks and limitations
Spirometry is safe, though the forceful blowing can occasionally cause brief dizziness or coughing. Good results depend on effort and technique, so clear instructions and sometimes repeat attempts are needed.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Spirometry (Lung Function Test): frequently asked questions
What does spirometry diagnose?
It helps diagnose and monitor conditions that affect airflow, such as asthma and COPD, by measuring how much and how fast you can breathe out. Results are interpreted with your symptoms and history.
How should I prepare for spirometry?
You may be asked to avoid certain inhalers, heavy meals, smoking or vigorous exercise for a period beforehand. Follow the specific instructions you are given so the results are accurate.
Related tests
Other other investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- UK National Screening Committee / relevant professional body
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