Getting a diagnosis

If you think you have asthma it is very important to make an appointment with your GP or an asthma nurse as soon as possible so they can discuss your symptoms, run through your medical history and do some tests. 

Asthma can be complex and can take time to diagnose. There is no definitive test.

First, your GP or asthma nurse will ask you lots of questions about your personal and family  history, your environment, your symptoms and your lifestyle to build up a good picture. Then they can assess how likely it is whether or not you have asthma.

Trial of treatment

If your GP or asthma nurse thinks a diagnosis of asthma is likely, they will probably prescribe a 'trial of treatment'. This is when you're given one or more asthma medicines to see if they help your symptoms. A trial of treatment lasts between two to eight weeks depending on what medicines you're given. Even if you don’t have asthma, these doses are very low and the benefits of taking the medicines, to see whether or not you have asthma, far outweigh any potential side effects.

If you respond to the trial of treatment, it is a very good indication you could have asthma. Your treatment is likely to be continued and you will be monitored to make sure you’re taking the lowest dose possible to manage your symptoms effectively.

If you don't respond to the trial of treatment, your GP will check your inhaler technique so that they can be sure you’ve been taking the medicine properly. If you haven’t been taking it correctly, you will probably be asked do another ‘trial of treatment’. If you have been taking it correctly, they may decide to do more tests. Depending on the results, your GP may need to investigate other possible causes for your symptoms. If it’s unlikely you have asthma, you may be referred to a specialist.

If at any point during the trial of treatment your symptoms get worse, contact your GP or asthma nurse without delay.


You may be asked to do a breathing test (lung function test) which measures how your lungs are working. Your GP or nurse will decide which test is suitable for you.

Your readings  help the GP or asthma nurse to make a diagnosis, but it is important to know that if you have a ‘normal' reading you may still have asthma. This is because the test is only one part of the picture and asthma symptoms are variable. For example, a normal reading at 4pm might have been lower at 9am that same day. Also, some test results may be affected if you’ve had a cold or virus in the past six weeks. In this case you may need to wait until you are better before you can have the test.

You may also be given a 'reversibility test' to work out whether your symptoms improve when you take asthma medication. This is where your GP or asthma nurse takes measurements before and after you take medication. There are various ways to carry out a reversibility test. Your GP or asthma nurse will choose the best way for you. 

Your GP or asthma nurse may also decide to carry out some other tests if necessary.

Asthma Diagnosis

If you are diagnosed with asthma, the good news is that there are some really effective medicines available to help manage your symptoms. When you’re first diagnosed, you will probably see your GP or asthma nurse a few times to check how you’re feeling and monitor your treatment, After that, it’s important that you book in a scheduled asthma review at least once a year even if your symptoms are well managed. This is so they can check your medicines in case the dose needs to be reduced or increased. It’s also an opportunity to discuss your triggers, lifestyle and any other factors that may affect your asthma, such as hayfever.

You are four times less likely to have an asthma attack if you have a written asthma action plan. You can take it to each review. 

If you’re worried about anything, speak to your hospital doctor, GP, asthma nurse or pharmacist. You can also call our UK Helpline on 0300 222 5800 (open Monday to Friday, 9am – 5pm). If you’re unsure about your diagnosis or medication, there’s a useful Q&A here.

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