What to Expect From a Spirometry Test

This pulmonary function test is used to diagnose lung diseases

Man using spirometer

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Spirometry, a type of pulmonary function test (PFT), is a non-invasive procedure that can provide information about how well your lungs are working. It measures how much and how quickly the air you exhale (breathe out) moves as you breathe into a tube. Spirometry is used to diagnose respiratory conditions such as asthma, and to monitor lung diseases to evaluate how well treatment is working.

Sometimes spirometry is done in conjunction with other PFTs.

what to expect during a spirometry test
Illustration by Emily Roberts, Verywell

Purpose of Test

Spirometry measures key aspects of pulmonary (lung) function. The test can play an important role in assessing many lung problems, and it's usually ordered by a pulmonologist, a physician who specializes In treating respiratory conditions.

It can help determine whether a lung condition is obstructive (in which exhalation is impaired) or restrictive (in which inhalation is impaired).

Spirometry is rarely used alone to diagnose a lung condition. It is typically combined with other findings, such as a physical exam, medical history review, and imaging tests, to reach a diagnosis.

As part of a panel of PFTs, spirometry may be used to help diagnose:

Spirometry is also useful for evaluating whether lung diseases are getting better, worse, or staying the same. This can help determine if a treatment is working or needs to be modified.

Spirometry may also be used before lung cancer surgery to predict how the lungs will function after a portion or lobe of a lung is removed.

Risks and Contraindications

Spirometry is a very safe procedure, but you may become short of breath or feel a little lightheaded while taking the rapid, deep breaths that are required. You may also experience coughing. These symptoms are normal and rarely a cause for concern.

People with asthma are at a small risk of an asthma attack during spirometry. In such instances, the exertion can cause temporary, sudden, and severe breathing problems.


People should not undergo a spirometry test if they:

There are certain conditions under which a person may not be able to breathe fully and deeply, potentially altering the accuracy of the test.

The conditions include:

  • Pregnancy
  • Stomach bloating
  • Extreme fatigue
  • General muscle weakness

While not necessarily contraindications, an evaluation from a healthcare provider may be required before the test can proceed.

Before the Test

Being aware of what's involved in a spirometry test can help you prepare and achieve the most accurate results.


A spirometry test typically takes around 45 minutes. It can take longer depending on waiting times. Ask your healthcare provider if the test may take longer so that you' can plan ahead.


Spirometry is usually done in a pulmonologist's office or at a hospital as an outpatient procedure.

In most cases, spirometry is performed by a pulmonary function technician or a respiratory therapist.

At-home spirometry testing machines are available for healthcare provider-supervised monitoring of a lung condition.

What to Wear

Because you will need to take very deep breaths, you should dress in loose-fitting clothing that won't restrict your breathing. Don't wear a belt or clothing that fits tightly around your chest or waist.

Food, Drink, and Medications

Little preparation is required before having a spirometry test. However, your healthcare provider may advise you to:

  • Eat lightly: If your stomach is too full, it may be harder to take deep breaths and you may end up vomiting.
  • Avoid alcohol before the test: You may not be able to breathe as well if you have alcohol in your system.
  • Check that your medications won't interfere with the test: Certain medical treatmrents can affect breathing, particularly inhaled bronchodilators. Avoid short-acting inhalers six to eight hours before testing unless you really need them (report any usage to the technician once you arrive).

Cost and Health Insurance

If you have health insurance, a spirometry test that's considered medically necessary will be partially or fully covered, depending on the terms of your policy. You also may be responsible for a co-pay or coinsurance. Prior authorization may be needed.

If you don't have insurance, your out-of-pocket cost for a spirometry test can range from $40 to $800, depending on where you are having the test and the tests that are done.

What to Bring

Bring your insurance card, ID, and form of payment to your spirometry test appointment.

Other Considerations

Here are a few other things you should do before having a spirometry test to ensure the most accurate results:

  • Go to bed early enough to get plenty of rest.
  • Do not smoke for at least four to six hours before the test.
  • Avoid heavy exercise or vigorous activity at least 30 minutes prior to testing.

During the Test

Here is a step-by-step description of what you are most likely to experience during a spirometry test, keeping in mind that there may be differences in equipment. Speak with your healthcare provider in advance to better gauge your expectations.


After you arrive for your appointment, you will check in. This may involve filling out consent forms, having your insurance card photocopied for your files, and taking care of your co-pay if you have one.

When you are called for your test, you will be asked to empty your bladder. You will then be escorted to the room where PFTs are performed. The technician or respiratory therapist will typically record your height and weight since these measures will influence how the tests are interpreted.

You'll be instructed to loosen your belt, if wearing one, and to remove any clothing or jewelry that restricts breathing. If you wear dentures, you will leave them in for the test.

Throughout the Test

You will be seated in a chair for the spirometry test and asked to sit and breathe normally to settle in. When ready, the technician will place a clip on your nose so that you only breathe through your mouth.

Most likely you'll be given a tube-like mouthpiece to breathe into. This will be connected to a spirometer, a machine roughly the size of a home printer that measures the force and volume of your breaths. Less commonly, there are portable devices about the size of a camera with a mouthpiece and digital read-out.

The technician will give you specific instructions on how to place your lips around the mouthpiece to create a tight seal. You will then be asked to take as big and deep a breath as possible and to blow into the tube as forcefully as you can.

The spirometer will create a graph that records the speed and amount of air as you breathe. To be considered accurate, the tests must be reproducible (meaning the same results are achieved repeatedly). So you'll be asked to repeat the test a minimum of three times.

Among the things that can potentially alter results:

  • Not having an adequate seal around the mouthpiece or placing the tongue incorrectly.
  • Not fully understanding the instructions, including pre-test preparations.
  • Coughing during inhalation or exhalation.
  • Not putting enough force into the exhalations (some diseases cause worsening pain with forceful breaths).
  • The mouthpiece was warped or damaged.

If there are signs of respiratory obstruction, a short-acting bronchodilator like albuterol may be used on a second round of testing to open the airways and see if the results improve.

If you feel dizzy or lightheaded, or can't stop coughing, let the technician know. In most cases, all you will need is a short break to recover.

After a spirometry test, you can return to your normal activities and use any medications you may have stopped.

Interpreting Results

Since the results of your test are immediately available, your healthcare provider will likely be able to review them with you at your appointment.

Spirometry provides two important measurements of lung function:

All three FEV1 measurements and all three FVC measurements must be within 200 milliliters (ml) of each other. If they aren't, the test will not meet the reproducibility criteria, and you may need to start all over again.

When the healthcare provider is satisfied that the test results are valid, the information will be used to determine if lung function is normal or abnormal.

Abnormal results indicate one of three possible breathing patterns:

  • Obstructive
  • Restrictive
  • A combination of both

Obstructive Disease

Obstructive lung disease is one in which damage to the lungs and narrowing of the airways make it harder to exhale. An obstructive pattern is seen in lung conditions such as COPD and asthma.

When the airways are obstructed, the amount of air you can exhale in one second (FEV1) is less than would be expected for someone your age, height, and weight.

FEV1 Value Indication
Greater than 80%  Normal
60% to 79% Mild obstruction
40% to 59% Moderate obstruction
Less than 40% Severe obstruction

With obstructive disease, the ratio of FEV1 to FVC (FEV1/FVC ratio) will be also lower than average.

Restrictive Disease

A restrictive lung problem means that the lungs contain too little air and do a poor job of transferring oxygen into the blood. Restrictive diseases are most often the result of a condition causing stiffness in the lungs.

Restrictive lung disease is sometimes associated with chest surgery, obesity, scoliosis (abnormal curvature of the spine), sarcoidosis (an inflammatory disease that causes abnormal growths in tissue), and scleroderma (the abnormal, unprovoked buildup of scar tissue).

A restrictive pattern will be indicated by:

  • A low FVC
  • A normal FEV1/FVC ratio (meaning that both values are proportionately decreased)

Obstructive/Restrictive Disease

A combination of both obstructive and restrictive breathing patterns may be seen when a person has more than one lung disease, such as cystic fibrosis with asthma or sarcoidosis with COPD.

If you have COPD, the results of a spirometry test after the use of a bronchodilator can establish how severe your disease is and whether or not it is progressing.

If the second round of spirometry testing using a bronchodilator improves your values by 12% or more, your healthcare provider can confidently conclude that you have asthma.


If your spirometry test results don't help determine if an obstructive and/or restrictive lung disease is involved, your healthcare provider may order other PFTs, such as plethysmography, to measure your total lung capacity.

If a definitive diagnosis is reached, the next step would be to address treatment options and, in some cases, undergo additional tests to characterize and stage the disease.

Home Spirometry

A home spirometry unit—basically a scaled-down version of the type used in clinical settings—can be useful under certain circumstances with the oversight of a healthcare provider.

A home device allows you to regularly monitor trends in your breathing patterns over a period of time to report back to your practitioner. This information may help your medical professional to fine-tune your treatment more precisely than is possible with a single office visit.

On the downside, the accuracy of home spirometry units can vary by brand. Cheaper ones tend to be less accurate, while recommended ones can often be unaffordable. Your healthcare provider can recommend the unit best suited to your condition. Home spirometers are sometimes covered by insurance, at least in part, if medically indicated.

It's important not to use a home spirometer as a substitute for regular medical visits or to make your own treatment changes based on the readings.

Note that there is a simpler type of spirometer called an incentive spirometer that does not provide measurements of lung function. It's a device designed to help keep the lungs clear after surgery.

A Word From Verywell

If you have undergone a spirometry test, you can ask your healthcare provider to explain the findings to you, what the numbers mean, and if there have been any changes in value since your last visit. The results of your test, along with your symptoms, can help In the diagnosis of your breathing problem. And changes to your test results over time may help guide your treatment.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Pat Bass, MD
Dr. Bass is a board-certified internist, pediatrician, and a Fellow of the American Academy of Pediatrics and the American College of Physicians.