You need to know your personal best peak flow number to help control your asthma. Changes from your
personal best can help you see how well your asthma is under control. These changes also can let you
know when you need medication and when you need medical care. This calculator will determine your Green,
Yellow and Red Zones, based on your personal best peak flow number.
If you don't know your personal best peak flow number, or don't know how to find it, click here for an
Each person's asthma is different, and each person's personal best peak flow number is different.
Even among people of the same height, weight and sex, peak flow numbers can differ.
Here's how to determine your personal best peak flow number:
Talk to your doctor before measuring your personal best peak flow number. He or she may have
other instructions or suggestions, based on your condition.
Once you know your personal best peak flow number, you can use this calculator or ask your doctor
to help determine the values for your Green, Yellow and Red Zones.
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Your Green Zone is above percent. (80 to 100 percent of your personal best)
What the Green Zone means:
The Green Zone is a sign that your asthma is in good control. It means you currently have no symptoms of asthma. You should continue to take your medication as usual.
Your Yellow Zone is below percent. (50 to 79 percent of your personal best) liters/minute.
What the Yellow Zone means:
The Yellow Zone is your caution signal. It means you need to take your quick-relief medicine from the instructions on your written asthma plan of action. The Yellow Zone also means your asthma may not be in good control. Ask your doctor if you need to change or increase your daily medications.
Your Red Zone is anything below percent. (Less than 50 percent of your personal best)
What the Red Zone means:
The Red Zone is your emergency signal. Take or increase your quick-relief medicine immediately, according to the instructions on your written plan of action. Then, call your doctor to find out what to do.
National Center for Biotechnology Information
This calculator is not intended to replace the evaluation of a health care professional.