Skip to Content

How To Use A Peak Flow Meter


What is a peak flow meter?

A peak flow meter is a small handheld device that measures how well your lungs are working. It measures how much and how fast you exhale after you take a deep breath in and blow out as hard as you can.

How does a peak flow meter help to manage asthma?

You can use a peak flow meter to:

  • Monitor how well your lungs are working: Peak flow numbers will help you know how and when to take your medicine. Peak flow numbers will help you know when to call your caregiver or seek care immediately.
  • Find out if treatment is working: Over a period of time, the peak flow number may tell your caregiver if your asthma action plan is working. It may also tell caregivers if you need more or less medicine.
  • Alert you to an asthma attack: Daily peak flow readings may help you know if you are having early signs of an asthma attack. Your peak flow number may decrease a few hours or days before an asthma attack. You may notice this decrease when you compare daily peak flow readings.
  • Help find your triggers: Your peak flow numbers may decrease when you have been exposed to an asthma trigger, such as pollen or mold.

How do I use a peak flow meter?

Your caregiver will tell you where you can get a peak flow meter. It is important to learn to use it correctly. Record your peak flow values and bring these numbers to follow-up visits.

Peak Flow Meter
  • Slide the indicator tab to the bottom of the scale (zero) on your peak flow meter.
  • Stand up straight. Remove any gum or food from your mouth.
  • Take a deep breath. Put the meter into your mouth and close your lips around the mouthpiece. Make sure there are no gaps. Do not put your tongue over the hole.
  • In one breath, blow out as hard as you can into the mouthpiece.
  • Look at the numbered scale. Write down the number where the indicator tab stopped.
  • Repeat all the steps above 2 more times. Write down the numbers each time.
  • Record the highest of the 3 numbers.
  • Measure your peak flow rate twice a day, once in the morning and once in the evening.

What is my personal best peak flow number?

It is important to know your personal best peak flow number. This is the highest peak flow number you have had over a 2-week period during good asthma control. This means that during this time you are not having any symptoms. Take your peak flow reading twice a day for 2 weeks, or the length of time your caregiver tells you to. Your caregiver may also have you take a peak flow reading after you take medicine. Your personal best peak flow number is the highest number recorded during the 2-week period. Your personal best peak flow number will help caregivers develop an asthma action plan for you.

What is the peak flow zone system?

Peak flow numbers are put into zones like the colors of a traffic light. Your caregiver will give you numbers for each zone based on your personal best peak flow number. High numbers are green, low numbers are yellow, and dangerous numbers are red.

  • Green: This means that your asthma is in good control and that you have no asthma symptoms. Continue taking your medicine as directed. You do not need to change your medicines.
  • Yellow: This means to use caution. In this zone, you should be watchful for an asthma attack. You will need to follow your asthma action plan or directions from your caregiver. You may need to increase how often or how much medicine you take. It may also mean that your asthma is not completely under control. Caregivers may need to change your medicines or other treatments.
  • Red: This zone means danger and may be an emergency. Contact your caregiver or seek care immediately if you are in this zone.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your caregivers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

© 2015 Truven Health Analytics Inc. Information is for End User's use only and may not be sold, redistributed or otherwise used for commercial purposes. All illustrations and images included in CareNotes® are the copyrighted property of A.D.A.M., Inc. or Truven Health Analytics.