FEV1 helps measure the progression of lung conditions such as chronic obstructive pulmonary disease (COPD) or asthma. FEV stands for forced expiratory volume, which is the air you exhale in one second. A low FEV1 suggests a breathing obstruction.
Having trouble breathing is a hallmark symptom of COPD. COPD causes air to get trapped in your airways,
FEV1 is 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.
Read on to learn what your FEV1 score can mean and how it’s used to diagnose COPD, asthma, or rarer types of lung diseases.
Healthy values for FEV1 vary from person to person. They’re based on standards for an average person of that age, race, height, and gender. Each person has a predicted FEV1 value.
You can get a general idea of your predicted value with a spirometry calculator. The Centers for Disease Control and Prevention (CDC) provides a
If you have already received a COPD or asthma diagnosis, your FEV1 score can help determine your condition’s stage. This is done by
A doctor will calculate a percentage difference to compare your FEV1 score and predicted value. This percentage can help stage COPD.
According to the COPD GOLD guidelines from 2024:
| GOLD stage of COPD | Percentage of predicted FEV1 value |
|---|---|
| mild | 80% |
| moderate | 50%–79% |
| severe | 30%–49% |
| very severe | less than 30% |
For asthma, there are similar guidelines. They are:
| Asthma stage | Percentage of predicted FEV1 value |
|---|---|
| mild | >80% |
| moderate | 60%–79% |
| severe | <60% |
Your FEV1 score alone isn’t used to diagnose COPD or asthma. A diagnosis requires a calculation involving FEV1 and another breathing measurement called forced vital capacity (FVC). FVC
If a doctor suspects you have a lung condition, they’ll calculate your FEV1/FVC ratio. This represents the percentage of your lung capacity you can expel in one second. The higher your percentage, the larger your lung capacity and the healthier your lungs.
A doctor may also:
- 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 and your spirometry test will help establish the overall grade and severity.
- Look at other criteria to make a diagnosis of either COPD or asthma. This includes taking your detailed history, including whether you smoke, have had occupational exposure to a chemical or pollutant, and more.
- Complete other exams. This may include a physical exam, chest X-ray, or CT.
- Observe your reactions to certain medications. They make look at how you respond to certain inhaled medications.
It can be useful to monitor FEV1 over time for both COPD and asthma.
COPD
COPD is a progressive condition, which means that it will typically worsen over time. A doctor will monitor your symptoms with a spirometry test, usually once a year, to determine how quickly the condition is progressing.
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, a 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 mucus 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 due to long-term exposure to lung irritants other than smoke. This includes exposure to air pollution, chemical fumes, cooking fumes, and dust.
People who smoke 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.
Asthma
In cases of asthma, a doctor may ask you to start using inhaled bronchodilator medications, after which they will want to recheck your FEV1 to see if your percentage improves.
Since asthma symptoms can be improved, if your second and subsequent spirometry readings show at least a
If there is no improvement, a doctor may try to switch your medications. If there is still no improvement, they may suspect you have, in fact, a different condition like COPD.
A doctor will also look at your symptoms to check for improvement. Asthma symptoms include:
- coughing
- chest tightness
- breathing difficulty
- speaking difficulty
- fatigue
Asthma can be genetic or triggered by environmental factors like allergens. Some people do not experience breathing problems but only a chronic cough. This is known as couch-variant asthma.
FEV1 measures the stage of certain lung conditions like COPD and asthma. It indicates how much air you can exhale in one second, and a low FEV1 implies that your airflow is obstructed.
A doctor will assess your FEV1/FVC ratio if they suspect you have a lung disorder, which helps them form a diagnosis. The larger the percentage, the healthier your lungs and airway are.