FeNO (fractional exhaled nitric oxide) is a test to measure the levels of nitric oxide in your breath. A high level of nitric oxide when you breathe out can show that your airways are inflamed. This could be a sign that you have asthma.
A FeNO test is suitable for adults and most children over five.
Before your test, you should avoid the following as these can affect your results:
- too much physical activity or exercise for at least an hour before the test
- smoking for at least an hour before the test, if you smoke
- hot drinks, caffeine and alcohol for at least an hour before the test
- foods such as green leafy vegetables and beetroot for at least three hours before the test.
You can take your regular medicines as usual before the test. But let the person doing the test know about any medicines you’ve taken. You should also leave enough time to get to your appointment, so you’re not rushed and tired before the test.
View our videos to learn what to expect during your FeNO appointment.
Adult FeNO test:
Child FeNO test:
