Place the mouthpiece in your mouth and close your lips around it. Do not put your tongue inside the hole. Blow out as hard and fast as you can in a single blow. Write down the number you get. But if you cough or make a mistake, don't write down the number.
Repeat steps one through five again.
During the course of the day, repeat steps one through five and record the best of the three blows in your asthma diary. Good control is when you feel good and are symptom-free. Each patient's asthma is different, and your best peak flow may be higher or lower than the peak flow of someone of your same height, weight and sex. This means that it is important for you to find your own personal best peak flow number. Your treatment plan needs to be based on your own personal best peak flow number.