You may find it convenient to classify your PEFRs into Zones. The Zones are divided into three groups:
The ability to achieve 80% or more of your best PEFR. This means your asthma appears to be under good control, and you need not increase your medications unless you are having asthmatic symptoms.
PEFR values are between 50 to 80% of your best PEFRs. This indicates your asthma is under poor control even if you feel OK. You should increase your asthma medications according to the plan provided by your asthma specialist, check that all your asthmatic triggers are eliminated, and speak to your asthma specialist.
Your PEFRs have fallen below 50%. This is an urgent problem, and you should start your emergency medication and call the asthma specialist. If you do not respond to medications, you may need to go to the emergency room.