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Controlling Severe Asthma

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Asthma Classifications by Severity

Medically Reviewed By William C. Lloyd III, MD, FACS
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Classifying asthma into four categories according to its severity helps your doctor determine which treatments may work best for you.


According to the Centers for Disease Control and Prevention (CDC), more than 20 million adults and 4 million children in the United States live with asthma. This common medical condition causes your airways to swell in response to certain triggers, like allergies or smoke. If you have asthma, your airways also make extra mucus, making it harder to breathe. Your symptoms may include wheezing, coughing, and shortness of breath.

You may think all asthma is the same, but asthma is actually classified into four categories. If you have asthma, your doctor will decide how severe your condition is based on your unique medical history, a physical examination, and your symptoms. Also, your doctor may perform certain diagnostic tests to help determine your asthma severity.

How asthma severity is determined

Asthma severity is classified according to how serious your symptoms are and how frequently they occur. To help determine the severity of your asthma, your doctor may suggest a spirometry test in addition to a physical examination and discussion of your symptoms. Spirometry is a simple test used to determine how well your lungs work. In particular, your doctor may focus on your forced expiratory volume in one second (FEV1) results. This is the maximum amount of air you can force out of your lungs in one second. Lower than normal FEV1 results indicate obstructions or swelling preventing air from leaving your lungs.

If your asthma is classified as severe, it may be considered eosinophilic asthma, due to an abundance of white blood cells called eosinophils. If your doctor suspects this is the case, you will likely get a blood test to determine your eosinophil levels.

Currently, asthma is categorized into four groups, each of which is characterized by specific features.

Intermittent asthma

  • Symptoms occur less than twice each week.
  • Rescue inhalers are used less than twice each week.
  • Nighttime symptoms occur less than twice each month.
  • No interference with normal activities.
  • FEV1 is 80% or greater.

Mild persistent asthma

  • Symptoms occur more than twice each week.
  • Rescue inhalers are used more than twice each week, but not every day.
  • Nighttime symptoms occur three or four times each month.
  • Minor interference with normal activities.
  • FEV1 is 80% or greater.

Moderate persistent asthma

  • Symptoms occur every day.
  • Rescue inhalers are used every day.
  • Nighttime symptoms occur more than once every week, but not every night.
  • Some interference with normal activities.
  • FEV1 is 60 to 80% of normal lung function.

Severe persistent asthma

  • Symptoms occur multiple times every day.
  • Rescue inhalers must be used several times throughout each day.
  • Nighttime symptoms occur most nights of the week.
  • Extreme interference with normal activities.
  • FEV1 is less than 60% of normal lung function.
  • Standard medications aren’t controlling symptoms at the highest possible doses.
  • Eosinophil levels are elevated in the blood.

Asthma action plans

Asthma can cause exacerbations, or attacks, that are much more serious than your typical asthma symptoms. That’s why it’s important to create an asthma action plan with the help of your doctor. While you have a regular treatment regimen that includes certain asthma control medications, an asthma action plan helps you know which rescue medications to use in the event of an asthma emergency.

Your personalized action plan lists your rescue medications, what dose you should take, and when you should contact help for emergency medical treatment. It’s important to have your action plan readily available if you have an asthma attack.


Living with asthma can be challenging, but determining your asthma severity can help guide treatment and allow you to live more days symptom-free. Your doctor can help you determine your asthma severity with a physical examination, a discussion of your symptoms, and lung function tests like spirometry.

If you have asthma, it’s important to follow your doctor’s recommendations for treatment, which are based off the severity of your asthma. Doing so can help keep symptoms at bay and help you live life to the fullest.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2022 Sep 2
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