A peak flow meter helps you check how well your asthma is controlled.

Use it every day, and keep track of the results to help your doctor learn about your asthma. This may also help you determine if your asthma is getting worse, even before you have symptoms.

First, move the marker to the bottom of the numbered scale.

Stand up straight with your head up, and take a deep breath. Fill your lungs all the way. (Standing helps you get more air in your lungs.)

Place the mouthpiece in your mouth, between your teeth. Close your lips around it. Do not put your tongue inside the hole or block the vents in the back.

Blow out as hard and fast as you can. You want to move the marker as far as you can with your breath, so concentrate on exhaling forcefully and quickly.

Move the marker back to the bottom, and repeat these steps two more times. If you cough or make a mistake, do not include this as one of your three tries.

Record the highest of the three numbers in your peak flow diary.

Check which zone corresponds with your highest score. Follow the plan developed by you and your doctor for the appropriate zone.

If your best effort is in the red zone, take your relief medication immediately and call your doctor or go to the emergency room.