Children's Hospital Colorado
Breathing Institute
Breathing Institute

How to Use a Peak Flow Meter Video

How to Use a Peak Flow Meter

A peak flow meter is a portable, easy to use tool that measures how well your lungs are working. A peak flow meter is a tool to help see if your asthma is controlled.


  1. Before each use, make sure the sliding marker is at the bottom of the numbered scale.
  2. Stand or sit up straight. Take a deep breath. Put the mouthpiece between your teeth and close your lips tight. Do not put your tongue into the mouthpiece.
  3. In one breath, blow out as hard and fast as you can. The sliding marker will move up the scale. Repeat this test three times. Record the HIGHEST of the three numbers on your peak flow chart.

When to use a Peak flow meter

  • When you first start checking your peak flow readings—take them daily for 2-3 weeks at the same time in the afternoon to help find out what your “Personal Best” number is.
  • When you have asthma symptoms, a cold, or other sickness that changes your breathing.
  • When you need to use quick-relief (rescue) medicine, like albuterol. Check your peak flow before you take your quick-relief medicine. Then check it again after 20 minutes.

When your Peak Flow Measurement is part of your Asthma Action Plan

Your Asthma Action Plan lists what medicines to take and when to take them. It uses three color-coded zones: green, yellow or red, like a stoplight. Symptoms and peak flow numbers can help you judge whether your asthma is controlled or not.

  • Green Zone: 80 to 100 percent of your “Personal Best” peak flow number. All systems "go." You are relatively free of symptoms. Keep up your current daily asthma plan.
  • Yellow Zone: 50 to 80 percent of your “Personal Best” peak flow number. "Use Caution," as your asthma is worsening. Use your quick-relief (rescue) medicine, like albuterol, and repeat peak flow. If still in the yellow zone, call your healthcare provider for help.
  • Red Zone: Below 50 percent of your “Personal Best” peak flow number. HEALTH ALERT! Repeat the use of your quick-relief (rescue) medicine, like albuterol. If you are still in the red zone, call your healthcare provider right away or go to a hospital ER.

Download instructions on how to use Peak Flow Meter (.pdf)

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