How Asthma Is Diagnosed

Asthma is diagnosed based on your symptoms, a physical exam, and various tests, including pulmonary function tests to evaluate breathing. Because the telltale symptoms of asthma, such as wheezing and shortness of breath, are common in other respiratory conditions, differential diagnosis also may be necessary to rule out causes other than asthma.

Female doctor assists young asthmatic patient
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Self Checks / At-Home Testing

Asthma is not a disease that can be self-diagnosed, but becoming familiar with the most common symptoms can alert you to the possibility you (or your child or other person in your household) might have asthma, in particular:

  • Wheezing: A high-pitched noise produced when you exhale
  • Shortness of breath (dyspnea): The feeling you can't catch your breath
  • Chest tightness that accompanies dyspnea
  • Cough: Dry, unproductive, and most common at night

If you develop these symptoms and they become frequent and persistent, make an appointment to see your doctor or a pulmonologist (a physician who specializes in respiratory diseases).

Before you see your doctor, begin keeping a written record of your symptoms. Jot down the nature of the symptom, when and where it occurs, and what you're doing at the time. Note, for example, if you experience symptoms when you dust, are around animals or smokers, or when there are changes in the weather (cold dry air is a common asthma trigger). This will reveal a pattern of asthma flare-ups that will help pin down your diagnosis and reveal what your asthma triggers may be.

Physical Examination

To diagnose asthma, your doctor will start by asking about your medical history and ongoing health issues. Asthma is especially common in people who have atopic conditions such as hay fever (allergic rhinitis) or atopic dermatitis. Your family health history will be important as well, as asthma tends to run in families.

They'll next want as many details about your symptoms as you can provide. This is when keeping a record of your symptoms can be invaluable. Also share with the doctor any changes you've made in your daily life that might have been prompted by asthma symptoms: Are you having groceries delivered because you feel winded when carrying packages or even walking around a store? Has your child had to sit out in gym class more often than not because of breathing difficulties?

The next step in diagnosing asthma will likely be a physical exam that focuses on your breathing. The doctor will listen carefully for wheezing, which isn't present all the time in people with asthma, but if it happens to occur during your appointment it will provide a strong clue as to your diagnosis.

The doctor will also check inside your nose for inflammation—swelling of the nasal cavities that can indicate allergic rhinitis.

Labs and Tests

If your doctor feels certain you have asthma, they may run certain tests to get more information about the type and severity of your condition.

Pulmonary Function Tests

These are quick, noninvasive tests that reveal how well your lungs are functioning:

  • Peak expiratory flow rate (PEFR): PEFR is a measurement of how powerfully you can exhale. This is gauged with a simple hand-held device called a peak flow meter. A normal PEFR is 80% or greater than what would be predicted for the person being tested.
  • Spirometry: A test that measures how much air you breathe in and out and how quickly.

Bronchodilation and Bronchoprovocation Tests

These tests gauge how well the lungs respond to either a quick-relief asthma medication or an intentional disturbance to normal airflow. They usually are done if spirometry is normal in spite of asthma symptoms.

  • Bronchodilator responsiveness testing: A bronchodilator is a fast-acting medication that provides quick relief of asthma symptoms. This test involves administering a bronchodilater and, 10 to 15 minutes later, repeating an initial spirometry test and comparing the results. If the medication brings about an increase in airflow of 12%, it is an indication that asthma is the cause of symptoms.
  • Bronchoprovocation challenge testing: This test involves inhaling either aerosolized chemicals or cold air, or performing exercises, to see if it induces asthma symptoms. By measuring lung function after exposure to these triggers, a doctor may be able to diagnose asthma.

Fractional Exhaled Nitric Oxide (FeNO) Test

If after routine testing, including spirometry and bronchodilator responsiveness, an asthma diagnosis isn't certain, a FeNO test may be performed, according to National Institutes of Health recommendations for asthma management. This test determines the presence of inflammation in the lungs and is performed using a portable device that measures the level of nitric oxide in parts per billion (PPB) in exhaled air.

Requirements for Asthma Diagnosis

An asthma diagnosis requires:

  1. Presence of symptoms compatible with asthma such as cough, wheezing, or shortness of breath.
  2. Objective measurement of decreased airflow in your lungs that either partially or completely improves spontaneously or with treatment.

Imaging

Most people with asthma have normal chest X-rays, but some doctors order them for patients who are experiencing wheezing for the first time. This is because if asthma has gone undiagnosed for a long time, a chest X-ray may reveal hyperexpansion (overinflated lungs).

Differential Diagnoses

Because wheezing can be symptomatic of diseases other than asthma, your doctor may need to rule them out in order to definitively diagnose asthma:

  • Gastroesophageal reflux disease (GERD): GERD may lead to wheezing and cough; it's also commonly responsible for nighttime symptoms. Patients commonly experience a painful burning sensation as well as a sour or bitter taste in the back of the mouth.
  • Congestive heart failure: This is condition where the heart's pump is failing and unable to provide adequate blood supply. In addition to asthma-like symptoms, there may be swelling in both legs and difficulty breathing while lying down.
  • Chronic obstructive pulmonary disease (COPD): A significant difference between COPD and asthma is that COPD often is characterized by a morning cough, while asthma symptoms can occur at any time and often only after exposure to triggers.
  • Pulmonary embolism (PE): The sudden onset of shortness of breath and chest pain are the most common symptom of PE, but the condition sometimes causes wheezing that could initially be mistaken for asthma.
  • Cystic fibrosis (CF): CF patients will wheeze, as well as experience shortness of breath and cough. However, this chronic illness is also associated with poor growth and a number of other problems in early childhood.

A Word From Verywell

Because asthma is a progressive disease—one that can worsen without treatment—it's imperative to see a doctor as soon as symptoms arise. An early diagnosis is key to effective treatment and preventing the disease from interfering with your quality of life.

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