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HealthInfo Canterbury

How to use a pulse oximeter for adults

A pulse oximeter is a small, painless device that clips on your finger and uses light beams in a sensor to estimate the amount of oxygen in your blood without taking a blood sample. This helps to track and assess how well your lungs are working.

A pulse oximeter can be used to help monitor a range of conditions in hospital or at home, including COVID-19.

COVID-19 is a viral infection. Most people have relatively mild symptoms, and they usually get better over two to three weeks. But some people have very serious symptoms, which can get worse quickly.

Recording your symptoms in a COVID-19 health and symptom diary can help you and your COVID-19 healthcare team track any changes in your symptoms and breathing.

A pulse oximeter measures two things.


Don't solely rely on a pulse oximeter to assess your health condition or oxygen level.

Other signs of low oxygen levels are:

If you experience any of these symptoms or your symptoms suddenly become worse, call 111 for an ambulance.

If you have any concerns or questions, contact your COVID-19 healthcare team.

Using a pulse oximeter

There are different brands of these devices – please read the manufacturer's instructions.

The following is a general guide. Ask your COVID-19 healthcare team if you have any questions.


Taking your reading

Recording your numbers

Pulse oximeter numbers

Your COVID-19 healthcare team will give you details on appropriate oxygen saturation levels for your specific medical condition. The following is a guide for adults with no previous lung conditions.

Oxygen saturation

Pulse rate
(bpm or PRbpm)


95 to 99

50 to 99


92 to 94

100 to 119

Seek advice from your COVID-19 healthcare team.

Below 92

120 or higher

Call 111 for urgent medical care.

If your oxygen saturation number drops by 3% or more from your first reading, contact your COVID-19 healthcare team.

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Content shared between HealthInfo Canterbury, KidsHealth and Healthify He Puna Wairoa as part of a National Health Content Hub collaborative. Last reviewed February 2022.

See also:

How to use a pulse oximeter in children

Page reference: 937755

Review key: HICOV-710714