How Asthma Is Diagnosed

Although you may receive an asthma diagnosis at any age, most people will be diagnosed in childhood. The classic signs of asthmawheezing, chest tightness, shortness of breath, and cough—can make the diagnosis difficult because they are general and non-specific. Your doctor will use a combination of a medical history review, physical exam, and testing to reach a diagnosis and rule out (or in) other conditions that may be mimicking asthma.

Self Checks/At-Home Testing

While you cannot diagnose yourself or your child with the condition, it is very helpful to be aware of the signs and symptoms of asthma and keep a record of those experienced. Note any factors that you think could have been involved—for example, you feel short of breath every time you dust. This diary may prove to be very valuable to your doctor.

As part of the diagnosis, or for ongoing checks, your doctor may have you perform at-home spirometry—pulmonary function testing that measures the amount of air you breathe in and out (and the speed at which you do so).

Only use a home spirometer if your doctor recommends it. Make sure you understand how to correctly use the unit you purchase and that you follow your doctor's instructions for reporting results accurately.

Intake and Physical Examination

In addition to checking for signs of breathing distress and response to allergens, your doctor will ask you questions about the symptoms you're experiencing and your medical history in an attempt to piece together pieces of the diagnostic puzzle.

Your doctor will carefully listen for wheezing that is typical of, but not specific to, asthma. Characteristically, it will be a high-pitched, almost musical instrument-like sound when you exhale. While this sign is not present all of the time in people with asthma, and it doesn't indicate the severity of the condition if you have it, detecting its presence is helpful in the diagnostic process.

The doctor will also check for nasal inflammation, which is a pale swelling of the nasal cavities that suggests allergic rhinitis that can worsen asthma symptoms.

The details you can share about your symptoms are important here, as some of the indicators of asthma are not ones that may be observed at your appointment. Your doctor will ask about:

  • Shortness of breath, which some may instead describe as chest tightness
  • Cough: Coughing that accompanies asthma is characteristically dry, non-productive, and often worse at night.
  • Circumstances that bring on symptoms: This is where you symptom diary comes into play. Typically in asthma, your symptoms will wax and wane over time. Your doctor will likely ask you to explain how quickly symptoms come on, if there's any predictability to them doing so, and what leads to the relief. They may also ask you to think about specific triggers of past symptoms, such as exposures to allergens like dust, pets, smoke, or changes in the weather, such as cold air.
  • Changes you've made: 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?

Asthma is more common in people with a family history of asthma or atopic diseases, so your doctor will also want to know if any of your relatives have:

  • Hay fever
  • Allergic rhinitis
  • Atopic dermatitis

A history of any of these conditions in a patient with symptoms compatible with asthma makes asthma much more likely.

Labs and Tests

If it is clear that your symptoms are due to asthma, your doctor may run test to help confirm a diagnosis or to get a more detailed report outlining what the problems are and how they have been resolved.

Pulmonary Function Tests

These are quick, noninvasive tests that give your doctor a sense of just how well your lungs are functioning:

  • Peak expiratory flow rate (PEFR): PEFR is a measurement of how hard you can exhale. This is gauged with a simple hand-held device called a peak flow meter. A normal PEFR is generally 80% of your predicted or greater. You will develop a personal best PEFR that will tell you how well your asthma is controlled. You and your physician will develop a plan for what to do if your PEFR is below 80% of normal. (You may or may not be asked to take these readings at home as well as in the doctor's office.)
  • Spirometry: While there are at-home spirometers, your doctor will also perform this test in the office with more advanced equipment. This test allows your doctor to better determine how severe your airflow obstruction may be and if you may benefit from asthma treatment.

Bronchodilation and Bronchoprovocation Tests

These tests gauge the lungs' response to either a quick-relief asthma medication or an intentional disturbance to normal airflow. This is usually considered if you have symptoms that suggest asthma, but you have normal spirometry testing.

  • Bronchodilator response: A characteristic of asthma is an improvement after treatment with a bronchodilator, a fast-acting medication. Generally, your doctor will repeat spirometry 10 to 15 minutes after treating you with a bronchodilator. Increases in the airflow of 12% are considered positive and assist in making a diagnosis of asthma.
  • Bronchoprovocation challenge testing: Just the opposite of looking for an improvement in lung function with a bronchodilator, bronchoprovocation testing attempts to provoke airflow obstruction after having you inhale an irritative substance. This testing is usually only done if you present with atypical symptoms.

Blood Tests

There are no diagnostic blood tests for asthma. Your health care provider may order some blood tests to help rule out other causes of your symptoms.

Requirements for Asthma Diagnosis

An asthma diagnosis requires evidence of:

  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.


Chest X-rays are usually normal in patients with asthma, but your physician may order one if you are presenting with wheezing for the first time. If asthma has gone undiagnosed for a long time, the chest X-ray may demonstrate hyperexpansion (overinflated lungs).

Differential Diagnoses

Asthma can sometimes be very tricky, as you may experience all of the possible symptoms or not at all. Furthermore, wheezing can accompany a number of other diseases as well. Your doctor will consider them as they work to make a diagnosis:

  • Gastroesophageal reflux disease (GERD): GERD may lead to wheezing and cough; it's also commonly responsible for nighttime asthma 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 some similar symptoms to asthma, patients have swelling in both legs and difficulty breathing while lying down.
  • Chronic obstructive pulmonary disease (COPD): COPD usually develops after age 40 and is primarily caused by damage from smoking. It has similar initial symptoms to asthma, such as wheezing, cough, chest tightness, and shortness of breath. One difference between COPD and asthma symptoms is that COPD often has a typical morning cough, while asthma symptoms can occur at any time of day and often do so only with exposure to triggers. While breathing returns to normal with asthma treatment, COPD results in a continued decline in lung function.
  • Pulmonary embolism (PE): A PE sometimes leads to wheezing, a classic asthma symptom, but sudden onset shortness of breath and chest pain are much more common.
  • 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

Being worried that you or your child has an asthma diagnosis can be a scary time. Knowing some of the questions your doctor may ask and some of the tests that may be ordered in diagnosing asthma will help you get the most out of your doctor's visit and alleviate some of the anxiety of the "unknown" that going to the doctor can create.

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