Back to Calculators
Asthma Zone Tool
About This Tool
This tool is for people with asthma. To use this tool, you must have a peak flow number. Your peak flow is how fast you exhale air after taking a deep breath. Your peak flow tells you and your doctor how well your lungs are working.
You need to know your best peak flow number to help control your asthma. Changes from your best number can help you see how well your asthma is under control. These changes also can let you know when you need medicine and when you need to see a doctor. This tool will show your Green, Yellow and Red Zones.
If you don't know your best peak flow number, or don't know how to find it, click here for an
How to Find Your Best Peak Flow Number
You will need to purchase a peak flow meter. You breathe into this meter. Then you write down the results.
Your best number is the highest number you can have over two to three weeks. You should take these numbers only when your asthma is in good control. Good control means you don't now have any signs of asthma.
Each person's asthma is different, and each person's best number is different. Even among people who are the same height, weight and sex, numbers can differ.
Here's how to determine your best peak flow number:
- Use the meter at least two times a day for two to three weeks.
- Use the meter when you wake up. Use it again between noon and 2 p.m.
- If you use medicine to help you breathe, use the meter before and after you use this medicine.
Talk to your doctor before you use the meter. Your doctor may have other instructions.
Once you know your personal best number, you can use this tool. Or you may ask your doctor to help find your Green, Yellow and Red Zones.
Close this section
Here are the numbers for your asthma zones.
Your Green Zone is liters/minute or greater.
What the Green Zone Means
The Green Zone is a sign that your asthma is in good control. It means you currently have no signs of asthma. You should take your medicine as usual.
Your Yellow Zone is from liters/minute to liters/minute.
What the Yellow Zone Means
The Yellow Zone means you need to take your quick-relief medicine right away. 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 medicine.
Your Red Zone is anything below liters/minute.
What the Red Zone Means
The Red Zone means you have an emergency. Take your quick-relief medicine right away. Then call your doctor to find out what to do, or go right to the emergency room.
National Institutes of Health, National Heart, Lung, and Blood Institute. National Asthma Education and Prevention Program, Clinical Practice Guidelines, Expert Panel Report 2, Guidelines for the Diagnosis and Management of Asthma. NIH Publication No. 97-4051, July 1997, page 39. Accessed at: http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf