Lung function tests and spirometry explained
Spirometry sounds technical, but the idea is simple. You breathe into a device as hard and as long as you can, and it measures how much air moves and how quickly.
The three numbers that matter most
FEV1 reflects how freely air leaves your lungs in the first second. FVC reflects total capacity on that breath. The FEV1 divided by FVC ratio helps separate narrowed airways from reduced volume.
Results are compared with predicted values for your age, height, sex and ethnicity, so your numbers are always read in context.
What the test feels like
You sit comfortably, seal your lips around a mouthpiece and follow coached instructions. Each blow takes a few seconds and is repeated to make sure the result is reliable.
Some people feel briefly lightheaded. We build in rests and stop if you are uncomfortable.
When to consider a test
Breathlessness that is new or worsening, a persistent cough, wheeze, a smoking history, occupational dust exposure, or monitoring of known asthma or COPD.
It is also commonly requested for fitness-to-train and occupational health assessments.
What spirometry cannot do
It does not diagnose asthma or COPD on its own. Diagnosis needs clinical assessment alongside the numbers.
It also will not explain chest pain or sudden severe breathlessness. Those need urgent medical attention.
In short
Spirometry is quick, painless and objective, which makes it one of the most useful respiratory checks available outside hospital.
This article is general information and does not replace individual clinical advice. If you have symptoms that concern you, speak to our team, your GP or call 111.
diagnostics service
Lung Function Test (Spirometry)
Simple, reliable lung function screening for clarity and confidence.