Lung function
Spirometry explained
The standard breathing test for asthma and COPD - blowing hard into a mouthpiece to measure airway narrowing.
Key facts
At a glance
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Preparation: you may be asked to withhold inhalers beforehand and avoid heavy meals, smoking and vigorous exercise on the day.
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On the day: you take a full breath and blast it out as hard and long as possible through a mouthpiece - repeated several times for consistency.
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Reversibility: the test is often repeated after a bronchodilator inhaler to see whether narrowing opens up - the signature of asthma.
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Results: key numbers (FEV1, FVC and their ratio) are available immediately; interpretation comes with the report.
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Follow-up: your GP, asthma nurse or a respiratory specialist uses the pattern to diagnose asthma or COPD and set treatment.
The full picture
What this test involves, and how to get it
Spirometry measures how much air you can force out of your lungs and how fast. After a full breath in, you blast out as hard and long as you can through a mouthpiece - technique matters, so a trained operator coaches you through at least three consistent attempts. Two numbers carry the story: FEV1, the volume expelled in the first second, and FVC, the total forced volume. A reduced FEV1/FVC ratio signals airway obstruction - the pattern of asthma and COPD - while a proportionately reduced FVC suggests restriction, pointing towards different diseases. Repeating the test 15 minutes after a bronchodilator inhaler tests reversibility: substantial improvement is the classic signature of asthma.
Spirometry is the gateway test for chronic cough, breathlessness, wheeze and smoking-related symptoms, and no COPD diagnosis is secure without it. NHS spirometry runs through GP practices and community clinics, though provision has been patchy since the pandemic and waits vary; hospital laboratories handle complex cases. Privately, spirometry is available within days at respiratory clinics and health assessment centres, often bundled with a same-visit respiratory consultation - useful when symptoms are ongoing and the treatment question is live. Follow the withholding instructions for inhalers precisely; a test taken two hours after salbutamol answers a different question from the one your clinician asked.
A quiet reminder
This guide is for information, not medical advice.
Your own clinician knows your history and can tell you which parts apply to you. Next review of this page: 2027-09-27.
Frequently asked
Common questions about Spirometry explained.
Quick, plain-English answers to what people ask us most.
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What is Spirometry explained?
Spirometry explained is a diagnostic test used to look at a specific part of the body or how it is functioning, helping doctors reach a clear diagnosis. It is usually requested when symptoms, an examination finding, or an earlier test result needs further investigation. Your doctor can explain exactly why it has been suggested in your case.
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Why would a doctor order Spirometry explained?
Doctors typically request this test to confirm or rule out a suspected condition, investigate unexplained symptoms, or monitor something that has already been diagnosed. It gives more detailed information than a standard examination alone can provide. The result helps guide what treatment or further investigation, if any, is needed.
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Do I need to prepare for Spirometry explained?
Preparation requirements vary by test; some need no special preparation, while others ask you to avoid caffeine, certain medications, or strenuous exercise beforehand. You will normally be given specific instructions when the appointment is confirmed. If anything is unclear, it is best to check directly with the clinic beforehand.
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What happens during Spirometry explained?
You will be asked to carry out a series of simple, guided steps - such as breathing into a device, lying still while readings are taken, or performing light activity - while equipment records the relevant measurements. The person carrying out the test will explain each stage as you go. Most appointments are completed within a single visit.
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Does Spirometry explained hurt or carry risks?
These tests are generally safe and non-invasive, with little to no discomfort involved. Any risks are usually minimal and will be explained to you before the test if relevant. Tell the team if you have any concerns so they can address them directly.
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How long do results take?
Results are usually reported by a specialist within a few days, though this can vary depending on the complexity of the test and whether further analysis is needed. You will normally be told when and how to expect your results at the time of booking. Urgent findings are typically flagged and communicated more quickly.
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What do abnormal results mean, and what happens next?
An abnormal result does not automatically mean something serious - it simply indicates that further assessment may be needed. Your doctor will review the findings in the context of your symptoms, history, and any other test results before recommending next steps, which might include further investigation, referral to a specialist, or reassurance that no action is needed. Always discuss your specific results with a doctor rather than interpreting them alone.
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Is Spirometry explained available privately, or should I wait for the NHS?
Spirometry explained can usually be arranged privately, often within days, with results reviewed by a specialist rather than waiting for routine NHS scheduling, which can take considerably longer depending on local demand. Cost varies by provider, and many private providers accept both self-referral and GP or specialist referral. Your GP can also advise on the appropriate NHS pathway if you would prefer to wait.
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Is Spirometry explained accurate and reliable?
This is a well-established test used routinely in clinical practice, and when performed and interpreted by an experienced specialist it is generally considered reliable. As with any test, results are always interpreted alongside your symptoms and medical history rather than in isolation. Occasionally a test may need to be repeated or supplemented with further investigation for a fully clear picture.
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How do I book Spirometry explained privately, and how quickly can I be seen?
You can typically book privately with or without a GP referral, and appointments are often available within a matter of days. A specialist reviews and reports the results, with a clear explanation of what they mean and any recommended next steps.