Spirometry (Lung Function Test)
A breathing test that measures how much air you can blow out and how fast, used to diagnose asthma and COPD.
Quick Summary
To diagnose and monitor asthma, COPD and other lung conditions.
FEV1, FVC and their ratio.
Avoid inhalers for the time advised, smoking and heavy meals before the test.
Overview
You take a deep breath and blow out as hard and fast as you can into a mouthpiece.
A reversibility test repeats it after an inhaler.
What It Measures
FEV1
Air blown out in one second.
FVC
Total air blown out.
FEV1/FVC
Ratio showing airway narrowing.
How It's Performed
- 01
Instructions
A nose clip and mouthpiece.
- 02
Blow
Several hard, long breaths out.
- 03
Repeat
Sometimes after an inhaler.
Reference Ranges
Note: Normal ranges vary by laboratory. Consult your report for the specific reference used.
| Parameter | Typical Range (Adult) | Units |
|---|---|---|
| FEV1/FVC (adults) | Above 0.70 | ratio |
Interpreting Results & Next Steps
Discuss with Doctor
Your doctor will explain the report and what happens next.
If values are Low:
A ratio below 0.70 suggests airway narrowing, as in COPD.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Lung Function Tests(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Spirometry(opens in a new tab) · NHS