To diagnose asthma, physicians rely on a combination of medical history, physical exams, and laboratory tests. These tests may include:

• Spirometry—a simple test to measure lung function that involves a patient exhaling into a device called a spirometer. Spirometry can be used to:
  
  Determine how well the lungs receive and hold air
  Monitor lung disease
  Monitor the effectiveness of treatment
  Determine the severity of a lung disease
  Determine whether the disease is restrictive, causing decreased airflow, or obstructive, causing disruption of airflow

• Peak Flow Monitoring—measures the fastest speed at which a person can blow air out of the lungs

• Inhalation Challenge—measures the response of your airways to substances that may be causing asthma

• Exercise stress test—determines the effect of exercise on lung function