Peak flow is a simple measurement of how quickly you can blow air out of your lungs. It's often used to help diagnose and monitor asthma.

A peak flow test involves blowing as hard as you can into a small, hand-held device called a peak flow meter.

These areavailable on prescription or can be bought from most pharmacies.

This page covers:

Why peak flow is measured

How to measure your peak flow

Your peak flow score

What to do if you peak flow is low

Content supplied by the NHS Website

Medically Reviewed by a doctor on 28 Nov 2016