Spirometry: What the Lung Function Test Measures, How It's Done and What Results Mean
Updated: 2 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review
Quick Answer: What is spirometry?
Spirometry is a safe breathing test that measures how much air you can blow out of your lungs and how fast. You take a deep breath and blow out hard into a mouthpiece connected to a spirometer. It helps diagnose and track asthma, COPD, cystic fibrosis and pulmonary fibrosis. The test takes 15 to 30 minutes and isn't painful. [1]
What the research says
Spirometry finds lung disease that people don't know they have. A meta-analysis of 26 studies found that 1 in 4 patients using inhaled medicines (25%) and 1 in 6 smokers (16%) met spirometry criteria for COPD without a COPD diagnosis. It also found that only 50% to 75% of people with a recorded COPD diagnosis showed airflow blockage on spirometry. (Perret et al., BMJ Open Respiratory Research, 2023) [2]
Low readings matter even when the pattern looks "normal." Pooling 8 population studies with 40,699 people who had preserved ratio impaired spirometry (PRISm), researchers found a 71% higher risk of death from any cause (hazard ratio 1.71) compared with people whose spirometry was normal. (Yang et al., European Respiratory Review, 2023) [3]
Many smokers screened for lung cancer have hidden airflow limitation. Across 42 studies and 72,209 people in lung cancer screening programs, 40.1% had airflow limitation, and 65.2% of those found by spirometry had not been recognized before. (Choi et al., Chest, 2025) [4]
Key takeaways
Spirometry measures how much air you can forcefully breathe out and how much you breathe out in the first second. [1]
It helps diagnose asthma, COPD, cystic fibrosis and pulmonary fibrosis, and it tracks lung disease over time. [1]
You blow into a mouthpiece at least three times; the whole visit takes about 15 to 30 minutes. [1]
A result of 80% or more of the expected value for someone like you is considered normal. [1]
The test is safe and not painful, though you may feel briefly dizzy, tired or short of breath. [1]
What is spirometry?
Spirometry (pronounced "spy-ROM-uh-tree") is a lung function test. It measures the air that flows in and out of your lungs and estimates how much air your lungs can hold. [1]
The test uses a spirometer, a mouthpiece attached to a computerized machine that records your airflow. A spirometer does not improve your lung function. It only helps your provider find out whether you have a breathing problem and how serious it is. [1]
Spirometry is also called a pulmonary function test or lung function test. [1]
Why is spirometry done?
Your provider may order spirometry to check whether your lungs are working as well as expected for someone like you. It can help: [1]
Diagnose conditions such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis and pulmonary fibrosis
Measure your lung capacity and track changes over time if you have a chronic lung condition
Find narrowed airways
Show whether inhaled medicines are likely to help your breathing
Check the effects of exposure to certain substances on your lungs
Estimate your risk of breathing problems before surgery
You may be sent for spirometry if you have symptoms such as shortness of breath, wheezing, a cough (especially one that brings up mucus), trouble taking a deep breath or a tight, painful feeling in your chest. [1]
Who performs spirometry?
A respiratory therapist, nurse, general practitioner or pulmonologist (lung specialist) can perform the test. It is done in a provider's office or in a lung function lab. [1]
How do you prepare for spirometry?
Preparation is simple. Your provider may ask you to: [1]
Stop certain breathing medicines for a short time before the test
Wear loose clothing that doesn't squeeze your chest
Avoid a large meal for at least 2 hours before the test
Avoid heavy exercise for at least 30 minutes before the test
Tell your provider if you have had a heart attack or have another heart condition, because blowing hard can raise your heart rate. [1]
What happens during spirometry?
The test follows a few simple steps: [1]
A soft clip is placed on your nose so you breathe only through your mouth.
You take the deepest breath you can.
You blow out as hard and as fast as you can into the spirometer.
You repeat this at least 3 times so the results are accurate and repeatable.
If your provider asks for it, you inhale a medicine that opens your airways (a bronchodilator), and then you do the test again so the two results can be compared.
The person running the test will coach you through each breath. The visit usually takes about 15 to 30 minutes. [1]
Spirometry at a glance
Item | Typical detail |
Where it's done | Provider's office or lung function lab |
Who does it | Respiratory therapist, nurse, general practitioner or pulmonologist |
How long it takes | About 15 to 30 minutes |
Number of attempts | At least 3 blows |
Does it hurt? | No |
When results arrive | Usually within a few days |
Sources: [1]
What does spirometry measure?
Spirometry gives two main numbers: [1]
Measurement | What it means |
FVC (forced vital capacity) | The most air you can forcefully breathe out after taking the deepest breath you can |
FEV1 (forced expiratory volume in 1 second) | How much air you breathe out in the first second of that forced breath |
Sources: [1]
Your results are compared with the typical values for people like you. These expected values depend on factors such as your sex. [1]
What do spirometry results mean?
A result of 80% or more of the typical value for someone like you is considered normal. Lower results can point to two main patterns of lung problems: [1]
Pattern | What it means | Examples of causes |
Obstructive | You have trouble breathing all the air out because of lung or airway damage | Asthma, bronchiectasis, COPD, cystic fibrosis |
Restrictive | Your lungs can't fully expand, so they hold less air | Interstitial lung disease, sarcoidosis, scoliosis, muscular dystrophy, ALS |
Sources: [1]
Results can also show a blockage in your airways, lung volumes that are lower than normal, how severe a lung disease is and whether it is getting worse over time. Your provider may order more tests, such as lung volume and diffusion capacity tests, to learn more. [1]
What are the risks of spirometry?
Spirometry is safe and isn't painful. Blowing out hard several times can make you feel: [1]
Dizzy or lightheaded
Tired or short of breath
Like coughing
These feelings usually pass soon after the test. Because the test can raise your heart rate, let your provider know about any heart condition before you start. [1]
What happens after spirometry?
You can go back to your normal activities, including exercise, right after the test. You can also restart any medicines you were asked to stop. [1]
A specialist reviews your results, and your provider usually contacts you within a few days. If you have a chronic lung disease, you may need lung function testing every year to track how your lungs are doing. [1]
When should you call your doctor?
Contact your provider if: [1]
You haven't heard about your results after a few days
You notice any change in your breathing
Questions to ask your provider
Why do I need spirometry, and what are you checking for?
Should I stop any of my breathing medicines before the test?
Will I have the test again after a bronchodilator?
Are my results normal for someone my age and sex?
Do my results show an obstructive or a restrictive pattern?
Do I need more lung function tests, and how often should I repeat spirometry?
Conclusion
Spirometry is a quick, safe breathing test that shows how much air you can blow out and how fast. It helps your provider diagnose conditions such as asthma, COPD and pulmonary fibrosis and track how your lungs change over time.
Preparation is simple: wear loose clothing, skip a large meal and heavy exercise beforehand, and follow any advice about pausing breathing medicines. Results usually arrive within a few days, and your provider will explain what they mean for you.
Keep learning: Read our guides to pulmonary function tests, asthma, COPD and the peak flow meter. For more on lung testing, see the American Lung Association's guide to lung function tests.
FAQ
What is spirometry used for?
Spirometry checks how well your lungs work and helps diagnose and track conditions such as asthma, COPD, cystic fibrosis and pulmonary fibrosis. [1]
Is spirometry painful?
No. You may feel briefly dizzy, lightheaded, tired or short of breath, or you may cough, but these feelings pass soon after. [1]
How long does a spirometry test take?
It usually takes about 15 to 30 minutes. [1]
How do I prepare for spirometry?
Wear loose clothing, avoid a large meal for 2 hours and heavy exercise for 30 minutes before, and ask whether to pause any breathing medicines. [1]
What is a normal spirometry result?
A result of 80% or more of the typical value for people like you is considered normal. [1]
What do FEV1 and FVC mean?
FVC is the most air you can forcefully blow out after a deep breath, and FEV1 is how much of it you blow out in the first second. [1]
What is the difference between obstructive and restrictive results?
An obstructive pattern means trouble breathing air out, as in asthma or COPD; a restrictive pattern means the lungs can't fully expand. [1]
Why do I inhale medicine during spirometry?
A bronchodilator opens your airways, and repeating the test afterward shows whether inhaled medicine improves your breathing. [1]
Can I exercise after spirometry?
Yes. You can return to your normal activities, including exercise, right after the test. [1]
When will I get my spirometry results?
A specialist reviews them and your provider usually contacts you within a few days. [1]
Related Reading
DLCO Lung Diffusion Test: Purpose, Normal Range and Results explains the breathing test that shows how well oxygen moves into your blood.
FEV1 (Forced Expiratory Volume): What Your Lung Test Numbers Mean explains the key spirometry number and what a low FEV1 means.
Learn more in our guide to Asthma: Symptoms, Causes, Triggers, Diagnosis & Treatment — Complete Guide.
Learn more in our guide to What Is Chronic Obstructive Pulmonary Disease (COPD)? Symptoms, Causes, Stages, and Treatment.
Learn more in our guide to Cystic Fibrosis: Symptoms, Causes, Diagnosis, and Treatment (2026 Guide).
Learn more in our guide to Pulmonary Fibrosis: Symptoms, Causes, Diagnosis, and Treatment Explained.
Learn more in our guide to Bronchiectasis: The Widened Airways Condition That Makes Mucus Hard to Clear — Explained.
Learn more in our guide to Interstitial Lung Disease: What It Is, What Causes the Scarring, and What Treatment Can Actually Do.
Body Plethysmography: What It Measures, How It's Done and Results explains the booth-based lung test that measures total lung capacity, residual volume and airway resistance.
Methacholine Challenge Test: How It Diagnoses Asthma, How to Prepare and What Results Mean explains the breathing challenge test used to confirm or rule out asthma.
References
Cleveland Clinic. Spirometry: Purpose, Procedure, Risks & Results. Cleveland Clinic. Last updated February 8, 2024. https://my.clevelandclinic.org/health/diagnostics/17833-spirometry
Perret J, Yip SWS, Idrose NS, et al. Undiagnosed and 'overdiagnosed' COPD using postbronchodilator spirometry in primary healthcare settings: a systematic review and meta-analysis. BMJ Open Respir Res. 2023;10(1):e001478. PMID 37130651. https://doi.org/10.1136/bmjresp-2022-001478
Yang S, Liao G, Tse LA. Association of preserved ratio impaired spirometry with mortality: a systematic review and meta-analysis. Eur Respir Rev. 2023;32(170):230135. PMID 37914194. https://doi.org/10.1183/16000617.0135-2023
Choi H, Kwak IY, Oh CR, et al. Prevalence of Airflow Limitation and Emphysema in Lung Cancer Screening Populations: A Systematic Review and Meta-Analysis. Chest. 2025;168(1):67-82. PMID 40054601. https://doi.org/10.1016/j.chest.2025.02.021
Medical disclaimer
This article is for general education only and does not replace advice from a qualified healthcare professional. Talk to your doctor about your own diagnosis and treatment, and seek emergency care right away for severe or sudden symptoms.
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