Asthma - Diagnosis - Diagnosis

Asthma is diagnosed based on your medical history, a physical exam, and results from diagnostic tests. You may need to see a team of healthcare providers, including your doctor; an asthma specialist, called a pulmonologist; or an allergy specialist, called an allergist.

Medical history and physical exam

Your doctor will ask about your risk factors for asthma and your symptoms. They may ask also about any known allergies. This includes how often symptoms occur, what seems to trigger your symptoms, when or where symptoms occur, and if your symptoms wake you up at night.

During the physical exam, your doctor may:

  • Listen to your breathing and look for symptoms of asthma
  • Look for allergic skin conditions, such as eczema

Diagnostic tests

Your doctor may ask you to perform the following tests to determine whether your symptoms are caused by asthma.

  • Pulmonary function tests, such as spirometry, which involves breathing in and out through a tube connected to a computer. This measures how much and how fast the air moves when you breathe in and out with maximum effort. Watch this video to learn more about taking a spirometry test.
  • Spirometry with bronchodilator tests to measure how much and how fast air moves in and out both before and after you take an inhaled medicine to relax the muscles in your airway.
  • Bronchoprovocation tests to measure how your airways react to specific exposures. During this test, you inhale different concentrations of allergens or medicines that may tighten the muscles in your airways. Spirometry is done before and after the test.
  • Peak expiratory flow (PEF) tests to measure how fast you can blow air out using maximum effort. This test can be done during spirometry or by breathing into a separate device, such as a tube.
  • Fractional exhaled nitric oxide (FeNO) tests to measure levels of nitric oxide in your breath when you breathe out. High levels of nitric oxide may mean that your lungs are inflamed. This test is done in adults and children age 5 and older. Read the FeNO fact sheet to learn more.
  • Allergy skin or blood tests, if you have a history of allergies. These tests can tell your doctor which allergens, such as pet dander or pollen, causes a reaction from your immune system.

Diagnosing asthma in children younger than 6

It can be hard to tell whether a child under age 6 has asthma or another respiratory condition, because young children often cannot perform a pulmonary function test such as spirometry. After checking a child’s history and symptoms, the doctor may try asthma medicines for a few months to see how well a child responds. About 40% of children who wheeze when they get colds or respiratory infections are eventually diagnosed with asthma.