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Obstructive sleep apnoea (OSA)

Diagnosing obstructive sleep apnoea (OSA)

If you think you, or someone you know, might have OSA, take a look at the Epworth Sleepiness Scale test. This helps to assess how likely you are to fall asleep in everyday situations.

Take the Epworth Sleepiness Scale test >

Take this along to your GP to talk about your symptoms and concerns. Your GP will ask about your symptoms, your health and your medical history, and about how sleepy you are when awake.

If your GP is not concerned, but you still are, keep trying to get a definite diagnosis. Ask to be referred to your local sleep service.

For support and advice, call our helpline on 03000 030 555.

Your GP might give you lifestyle advice about the best ways to get a good night’s sleep, lose weight and stop smoking.

If it is suspected that you might have OSA, you will usually be referred to a sleep clinic.

Going to a sleep clinic to diagnose OSA

In this section:

What happens at a sleep clinic?

Sleep clinics are specialist clinics that assess, diagnose and treat people with a range of sleep problems, including OSA.

Once you’ve been referred, you’ll be assessed. Clinics assess people in different ways. Some arrange for you to have an overnight sleep study at home before you visit, while others see you first before deciding if you need an overnight study.

Assessment and diagnosis of OSA at a sleep clinic

Clinics have at least one consultant and other staff, such as nurses and technicians. They will assess if you have OSA by asking questions and examining you. They will also ask you to complete a form about how sleepy you are – usually the Epworth Sleepiness Scale. They may also arrange a sleep study.

Questions about your medical history

This involves talking about your symptoms and quality of life. If you have a partner bring them with you, so they can report on what happens when you’re asleep. A good clinical history helps the doctor to reach a diagnosis. It may include questions about:

  • how long you sleep and the quality of your sleep
  • shift working (pattern and timing)
  • your symptoms and how long you have had them
  • your smoking history
  • family history of sleep disorders, such as OSA or narcolepsy
  • your mental health
  • any medication you use or have used
  • how sleepy you are and when you might fall asleep
  • the effect on your work and ability to concentrate

Examining you

This can include measuring:

  • your weight and height to find your body mass index (BMI)
  • your blood pressure
  • your neck circumference
  • your jaw size and position

and assessing:

  • your face and jaw appearance and symmetry
  • the airflow in your nose
  • your upper airway to see if it’s obstructed
  • your teeth and having a look at the size of your tongue
  • the inside of your mouth and upper airway

The clinic may also do a blood test.

What is a sleep study?

You’ll usually do a sleep study at home, using equipment lent to you for a night. But you may go to hospital overnight for a detailed study.

If you’re worried about the study, ask the sleep clinic what will happen. You can do some simple things to prepare, such as avoiding alcohol or caffeine and not taking a nap or strenuous exercise on the day. Let the clinic know if you’ve got any special requirements. If you’re ill on the date of your study, it’s best to postpone it until you’re feeling better.

For the study, you’ll be monitored as you sleep by equipment attached to you. This is completely painless and you’ll be able to roll over and change positions. You may be asked to sleep on your back for a while to see if this affects your breathing. If you’re in hospital and experiencing obvious signs of OSA, you may be woken up to use a continuous positive airway pressure (CPAP) machine, so you can be assessed with and without it.

There are different kinds of sleep studies used to diagnose OSA.


This measures the oxygen level in your blood. It’s often the first test for OSA, and is usually done in your home. You wear an instrument with a sensor called a pulse oximeter. This measures your blood oxygen level and your pulse. You’ll have a clip on your finger or earlobe and a device on your wrist.

What is a respiratory limited sleep study?

This overnight test can be done in hospital or at home. It measures your air flow, how your chest moves as you breathe, your heart rate and the oxygen level in your blood. Some devices register snoring sounds, body position and leg movements. Equipment will be attached to you with tape, wires and straps as you sleep.

What is polysomnography or PSG?

This is an overnight study, done in a quiet hospital room. It’s used when the results of other tests aren’t clear and in more complex cases. It assesses sleep and wakefulness by measuring your brain waves, eye movements and muscle movements. It also assesses your heart and lung function, by measuring your air flow, the movement of your chest, your oxygen levels and the activity of your heart activity. It films you while you sleep.

Reaching a diagnosis of OSA

Your doctor will diagnose you with OSA if the results of your assessment are clear.

If they aren’t, you may be asked to do more tests or to try a treatment called CPAP. If CPAP helps, OSA is the most likely cause of your symptoms.

Your doctor will want to see how severe your OSA is to find the best treatment for you. You may be told your OSA is mild, moderate or severe, depending on how many times you stop breathing in the night and your symptoms during the day. Once you’ve been diagnosed with OSA, it can be a relief. You now know why you’ve been so sleepy.

Next: Treatment for OSA >

We use your comments to improve our information. We cannot reply to comments left on this form. If you have health concerns or need clinical advice, call our helpline on 03000 030 555 between 9am and 5pm on a weekday or email them.

Download our OSA information (PDF, 229KB)

Last medically reviewed: March 2019. Due for review: November 2021

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.