Your FEV1 value is an important part of evaluating chronic obstructive pulmonary disease (COPD) and monitoring progression of the condition. FEV is short for forced expiratory volume. FEV1 is the amount of air you can force from your lungs in one second.

It’s measured during a spirometry test, also known as a pulmonary function test, which involves forcefully breathing out into a mouthpiece connected to a spirometer machine. A lower-than-normal FEV1 reading suggests that you may be experiencing a breathing obstruction.

Having trouble breathing is a hallmark symptom of COPD. COPD causes less air to flow into and out of a person’s airways than normal, making breathing difficult.

The normal values for FEV1 vary from person to person. They’re based on standards for an average healthy person of your age, race, height, and gender. Each person has their own predicted FEV1 value.

You can get a general idea of your predicted normal value with a spirometry calculator. The Centers for Disease Control and Prevention provides a calculator that lets you enter your specific details. If you know your FEV1 value already, you can enter it as well, and the calculator will tell you what percent of the predicted normal value your result is.

If you already received a COPD diagnosis, your FEV1 score can help determine which stage your COPD has reached. This is done by comparing your FEV1 score to the predicted value of those individuals similar to you with healthy lungs.

To make the comparison between your FEV1 score and your predicted value, your doctor will calculate a percentage difference. This percentage can help stage COPD.

According to the COPD GOLD guidelines from 2016:

GOLD Stage of COPDPercentage of predicted FEV1 value
mild80%
moderate50%–79%
severe30%–49%
very severeLess than 30%

Learn more about the GOLD guidelines for COPD »

Your FEV1 score on its own isn’t used to diagnose COPD. A COPD diagnosis requires a calculation involving both FEV1 and another breathing measurement called FVC, or forced vital capacity. FVC is a measurement of the greatest amount of air you can forcefully breathe out after breathing in as deeply as you can.

If your doctor suspects that you have COPD, they’ll calculate your FEV1/FVC ratio. This represents the percentage of your lung capacity that you can expel in one second. The higher your percentage, the larger your lung capacity and the healthier your lungs.

Your doctor will diagnose COPD if your FEV1/FVC ratio falls below 70 percent of the predicted value.

Your doctor will also likely use a COPD assessment test (CAT). This is a set of questions that look at how COPD affects your life. The results of the CAT, along with those of your spirometry test, will help to establish the overall grade and severity of your COPD.

COPD is a progressive condition. This means that over time, your COPD will typically worsen. People experience varying levels of COPD decline. Your doctor will monitor your COPD with a spirometry test usually once a year. They’ll monitor you to determine how quickly your COPD is worsening and your lung function is declining.

Being aware of your FEV1 score can help you manage your COPD. Experts make recommendations for the care of COPD based on these results. Between spirometry tests, your doctor may recommend rechecking your FEV1 whenever you see changes in your COPD symptoms.

Besides breathing difficulty, symptoms of COPD include:

  • coughing that produces a lot of mucous from your lungs
  • wheezing
  • tightness in your chest
  • shortness of breath
  • decreased ability to exercise or carry out routine activities

In most people, COPD is caused by cigarette smoking, but it can also occur as a result of long-term exposure to lung irritants other than smoke. This includes exposure to air pollution, chemical fumes, cooking fumes, and dust. Smokers may need to take more frequent spirometry tests because they’re more likely to experience faster and more frequent changes in lung capacity than nonsmokers.

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