2. Record how well your lungs are working

Your doctor may have you periodically record results of breathing tests (lung function tests). If your lungs aren't working as well as they should be, your asthma may not be under control. There are two main lung function tests:

• Peak flow. This test is done at home with a simple hand-held device called a peak flow meter. A peak expiratory flow measurement indicates how fast you can force air out of your lungs. Peak flow readings are sometimes gauged as a percentage of how your lungs work at their best. This is called your personal best peak flow.

• Spirometry. Spirometry tests can be done at your doctor's office with a machine called a spirometer. Some people use a hand-held spirometer to take measurements at home.

  Spirometry tests measure how much air your lungs can hold and how much air you can exhale in one second after you've taken a deep breath. This measurement is called forced expiratory volume (FEV1). Your FEV1 measurement is compared with the typical FEV1 for people who don't have asthma. As with your peak flow reading, this comparison is often expressed as a percentage.