In this section: Diagnosis and Lung Testing | How To Tell You Have Asthma | Your Healthcare Team

Only a healthcare professional can diagnose asthma. Conditions such as pneumonia, cystic fibrosis, heart disease, and chronic obstructive pulmonary disease (COPD) have to be ruled out before your doctor can be certain that you have asthma.

Symptoms observed upon physical examination, lung function testing, and medical and family history may all support a diagnosis of asthma. Other lung conditions have similar symptoms, which your healthcare practitioner may have to rule out. It is important to explain all of your symptoms and concerns and to ask any questions you may have. Something you think is not important may be useful in pinpointing a proper diagnosis.

Preparing for your appointment

You can get the most out of your time with your healthcare provider by planning carefully before you go.

Things you can do to prepare for your appointments include bringing:

  • A list of your most recent symptoms, including notes about whether they’ve changed since your last visit.
  • A record of your recent peak flow meter readings or symptom diary records.
  • Your Asthma Action Plan so that you and your healthcare provider can develop a plan. If you already have one, then bring it in case it needs to be modified.
  • Your inhaler(s) to review your technique.
  • A list of any questions you have. For example, you might ask: What makes my asthma worse? Is it okay to keep playing a sport? What should I do if I have an asthma attack?

Breathing Tests

To confirm a diagnosis, your healthcare provider will ask you to do breathing tests. They measure how well your lungs perform and to what degree asthma is affecting your breathing. These lung function tests include spirometry breathing tests and peak flow breathing tests.


Spirometry is a type of pulmonary function test (PFT) used to diagnose lung conditions like asthma and COPD. A spirometer measures the amount of air you can breathe out in one second and the total volume of air you can exhale in one forced breath.

When preparing for a spirometry test, your healthcare provider will give you detailed instructions prior to the test. Generally, you will be asked to refrain from using certain inhalers for a period of time prior to the test. If you are a smoker, you will be asked to refrain from smoking for a period of time prior to the test. 

How is a spirometry test performed?

  1. You will sit upright.
  2. You will be given a clip to place on your nose.
  3. You will be given a plastic mouthpiece connected to a spirometer.
  4. You will place the mouthpiece in your mouth and create a tight seal with your lips.
  5. You will take a deep breath in and then blow out as hard and fast as you can until you can’t blow out any more.
  6. You will do the test several times, until the best result is recorded.
  7. You will take some puffs of a bronchodilator medication.
  8. After 15 minutes, you will do the test again, to see if the medication helps your breathing. If your results are much better after taking the medication, you may have asthma.

Your healthcare provider will explain your results.

Some people who have asthma will have a normal spirometry test. If this is the case, you may be asked to take another test to confirm the diagnosis of asthma, like a methacholine challenge or exercise test.

*Infants and small children under 5-6 years old usually cannot do the spirometry test. Young children’s asthma is typically diagnosed based on signs and symptoms (including symptoms during playtime), family history, history of allergies, and their response to asthma medications.

Peak Flow Meter Test

A Peak Flow Meter estimates the Peak Expiratory Flow Rate, which is a measure of the fastest speed at which you can exhale the air from your lungs, after inhaling a big breath. The measurement relates to how well the air is moving through your airways, so if asthma is present with airway inflammation or bronchoconstriction, the peak flow levels will be lower. Three peak flows are measured in succession and the best reading is recorded.

Using the Asthma Monitor for these measurements allows you to monitor your asthma on a day to day basis and will help determine the effectiveness of prescribed anti-inflammatory (controller) medications.

If you are diagnosed with asthma, a healthcare practitioner will:

  • Create a customized treatment plan known as an Asthma Action Plan that fits your particular needs, lifestyle and triggers, as well as  the frequency and intensity of your symptoms.
  • If necessary, refer you to other healthcare professionals – individuals who can help you with specific aspects of asthma treatment and  management.
  • Recommend that you visit regularly so that your symptoms can be monitored and your treatment adjusted if necessary.


Find An Asthma Clinic Near You

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Asthma & Allergy HelpLine

Have questions about asthma diagnosis? Contact our free HelpLine service.

Learning To Live With Asthma

Newly diagnosed with asthma? Start here to learn about managing the disease.