How to use a pulse oximeter in adults

A pulse oximeter is a small device that fits on your finger and quickly and easily checks your oxygen levels and heart rate.

Note: The information on this page is for the use of a pulse oximeter in adults. For use in children, see how to use a pulse oximeter in children. 

A pulse oximeter can be used to help monitor a range of conditions in hospital or at home, including COVID-19 infection. COVID-19 is a viral infection. For most people, the symptoms are relatively mild, and they usually get better over 2 to 3 weeks. However, for some, the symptoms can be very serious and can get worse quickly.

  • Your healthcare team will let you know if you need a pulse oximeter at home. 
  • If you are advised to monitor your symptoms and breathing, then the use of a health and symptom diary can help you and your healthcare team track any changes.

This page will explain how to use a pulse oximeter, what the numbers mean and what actions you should take.

If at any time you experience shortness of breath at rest or difficulty breathing, or your symptoms become suddenly worse, call 111 for an ambulance.

What is a pulse oximeter?

Image of a pulse oximeter

A pulse oximeter is a small, painless device that clips onto 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 measures 2 things:

  • Pulse – this is a measure of how fast your heart is beating. Your pulse is measured in beats per minute (bpm). On your device this number may show as bpm or PRbpm (pulse rate/beats per minute).
  • Oxygen saturation level – this is a measure of how much oxygen is in your blood. Your oxygen saturation is measured as a percentage (scored out of 100). On your device this number may show as SpO2% (saturation percentage of oxygen).

How to use a pulse oximeter

There are different brands of these devices – please read the manufacturer's instructions. The following is a general guide. Ask your healthcare team if you have any questions.

How to use a pulse oximeter – a general guide

Preparing

  • Wash your hands and remove any nail polish or false nails. This allows the light beams in the sensor to measure through your fingernail.
  • Make sure you have been resting for at least 5 minutes before taking the reading.
  • If your hands are cold, warm them by rubbing them together.
  • Rest your arm and hand and keep them still while taking your reading.
  • Your hand should be at waist level, such as resting your hand on a table or the arm of your chair.

Taking your reading

  • Switch the pulse oximeter ON and the display will light up.
  • Squeeze to open and insert your finger until your fingertip touches the end.
  • It works best on the middle or index finger of either hand.
  • Keep your hand still and wait for 1 to 2 minutes until your pulse (bpm/ PRbpm) is steady and your oxygen saturation (SpO2%) number has not changed for 5 seconds or more.
  • If your numbers are not steady, try a different finger.

Recording your numbers

  • You should record the oxygen saturation number ‘SpO2%’ and the pulse rate number ‘PRbpm’ to track any changes. Here is a diary you can print and fill in.
  • Your heart rate and oxygen level numbers are easy to mix up. Be careful to record these correctly.
  • Measure and record your pulse (heart rate) and oxygen level 3 times a day at about the same time every day.
  • Your symptom diary is crucial to track any changes so your healthcare team can monitor you safely at home.
  • You should take extra measurements if you feel a change in your health.
  • To clean your device, check the manufacturer’s instructions.

What do pulse oximeter numbers mean?

Your 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
SpO2%
 Pulse rate (bpm or PRbpm) Action
95–99  50–99 ✔  Acceptable 
92–94  100 –119 Seek advice from your COVID-19 healthcare team
Below 92 120 or more Call 111 for urgent medical care

If your oxygen saturation number drops by 3 (ie, decreases by 3 %) or more from your first reading, phone the 24-hour COVID-19 number 0800 358 5453. 

Other signs or symptoms of low oxygen levels

Do not rely only on a pulse oximeter to assess your health condition or oxygen level. It is only a measurement device.

Other signs or symptoms of low oxygen levels are:

  • bluish colouring in your face, lips or nails
  • shortness of breath, difficulty breathing or a cough that gets worse
  • restlessness and discomfort
  • chest pain or tightness
  • fast or racing pulse rate.

If you have any concerns or questions, contact your healthcare team directly.

If at any time you experience any of the symptoms above, or your symptoms become suddenly worse, call 111 for an ambulance.

Learn more

Pulse oximetry British Lung Foundation, UK

References

  1. Pulse oximetry American Thoracic Society, US
  2. Pulse oximeter accuracy and limitations Food and Drug Administration, US
  3. Remote management of covid-19 using home pulse oximetry and virtual ward support British Medical Journal, 2021
Credits: Health Navigator Editorial Team. Reviewed By: Dr Helen Liley, Clinical Editor, Auckland Regional HealthPathways Last reviewed: 16 Oct 2021