Preparation is minimal for a pulmonary function test. Patients who are anxious about testing should be reassured that the procedures are painless, and that patients are allowed to rest between each phase of the testing if necessary. A physician may suggest the following preparatory steps:

• Do not eat a heavy meal before the test. A full stomach can keep the lungs from fully expanding.
  
  
• Do not smoke for four to six hours before testing. This can interfere with respiration during the test.
  
  
• Do not exercise for four to eight hours before the test. The can hamper breathing during the test.
  
  
• Patients should be advised not to use bronchodilators prior to testing. Such use can skew test results and mask potential problems.
  
  
• Tell the physician of any medications being taken prior to testing. Some medications, such as painkillers, can affect the results of the test.
  
  
• Use the bathroom just prior to testing.
  
  
• Wear loose clothing or loosen any tight-fitting clothing.

Those with dentures should wear them during testing. This will help form a seal around the mouthpiece used in the tests. 

If the patient being tested is a child, parents are encouraged to review the testing procedure with them in advance so they are not overly frightened by the testing itself.