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How to Use A Peak Flow Meter

Medically reviewed by Last updated on Oct 31, 2022.

What is a peak flow meter?

A peak flow meter is a handheld device that measures how much air you can breathe out when you exhale.

What is my personal best peak flow number?

Your personal best peak flow number is your highest peak flow number during good asthma control. Your healthcare provider will help you decide what your best peak flow number is. You should compare your daily peak flow numbers to your personal best peak flow number. This will help you and your healthcare providers know if your asthma is well controlled.

When should I use a peak flow meter?

  • Every morning before you take your asthma medicine
  • Before and after you take rescue medicine for an asthma attack or worsening symptoms
  • Other times during the day as directed by your healthcare provider

How do I use a peak flow meter?

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

  • 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. This is your peak flow number.
  • Repeat all the steps above 2 more times. Write down the numbers each time.
  • The highest of the 3 numbers is your best peak flow number.
    Peak Flow Meter

What is the peak flow zone system?

Peak flow numbers are put into colored zones like the colors of a traffic light. Your healthcare provider will tell you what your peak flow numbers are for each zone.

  • Peak flow numbers in the green zone mean your asthma is in good control . This is also known as the safety zone. Your treatment plan is helping to control your asthma. Continue taking your medicine as directed and stay away from asthma triggers.
  • Peak flow numbers in the yellow zone mean your asthma is not well controlled. This is also known as the caution zone. You may have shortness of breath, wheezing, or a tight chest. In this zone, you may be at risk for an asthma attack. You will need to follow your asthma action plan or directions from your healthcare provider. You may need to increase how often or how much medicine you take. Healthcare providers may need to change your medicines or other treatments.
  • Peak flow numbers in the red zone mean you are having an asthma emergency. This is also known as the danger zone. You may have severe shortness of breath or wheezing. Take your rescue medicine as directed and seek care immediately or call 911.

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 healthcare providers 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.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.