How to use a pulse oximeter in adults

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.  

The information on this page is about how to use a pulse oximeter with adults, read more about how to use a pulse oximeter in children.

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) or %SpO₂.
  
  

Image credit: Depositphotos

Note: Be aware that the quality and accuracy of different pulse oximeters can vary.

The level of oxygen in your blood can go down if your heart or lungs aren’t working well. This may be due to:

• an underlying condition (eg, a heart abnormality, heart failure or lung disease)
• a severe infection affecting your breathing
• being in an environment where there’s less oxygen in the air, such as at high altitudes 
• sleep apnoea – if you stop breathing while you’re sleeping this can lower the level of oxygen in your blood
• some medicines, such as anaesthetics.   

A pulse oximeter can be used to help monitor a range of conditions (including COVID-19) that can affect the level of oxygen in your blood. A pulse oximeter may be used in hospital, in an ambulance, or at home.

It can also be used by people doing very active sports or at high altitudes, such as when mountain climbing.

• If you're unwell, your healthcare team will let you know if you need a pulse oximeter at home
• If you're advised to monitor your symptoms and breathing, then the use of a health and symptom diary [PDF, 615 KB] can help you and your healthcare team track any changes. Often it's the change in oxygen levels that's as important as the level.

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

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

Video: How to use a pulse oximeter

(Healthify He Puna Waiora, NZ and Aotearoa Collaborative, NZ, 2021)

View transcript [DOCX, 37 KB]

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've 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 it 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 hasn't 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's a diary [PDF, 615 KB] 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. See the table below on what the pulse oximeter numbers mean and when to seek advice from your healthcare team. 
• Your symptom diary is very important as it allows you to track any changes so your healthcare team can monitor you safely at home.
• You should ask for help if you feel your health is getting worse.
• To clean your device, check the manufacturer’s instructions.

Your healthcare team will tell you what’s an appropriate oxygen saturation level for your specific medical condition. The following is a guide for adults with no previous lung conditions.  

• Oxygen saturation 95 to 100, pulse rate 50 to 99 – acceptable, no action needed.
• Oxygen saturation 92 to 94, pulse rate 100 to 119 – seek advice from your healthcare team.
• Oxygen saturation less than 92, pulse rate above 119 – get urgent medical help. 
  
  

Image credit: Healthify He Puna Waiora

Do not rely only on a pulse oximeter to assess your health condition or oxygen level. It's 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.

Pulse oximeters are very useful devices but it's important to remember that they have their limitations.

• Be aware that lots of different factors can affect the accuracy of a pulse oximeter reading. These include:
  • poor circulation
  • skin pigmentation/colouring
  • skin thickness
  • skin temperature
  • current tobacco use
  • use of fingernail polish or artificial nails
  • tattoos and dyes, and
  • maintenance and cleaning of devices.
• It's important that you learn how to use a pulse oximeter properly.
• Also be aware that not all pulse oximeters are of the same quality and accuracy. 

If you have any breathing problems or concerns, phone your healthcare team or HealthLine 0800 611 116 for advice. Don't rely on a pulse oximeter alone to assess your health condition or oxygen level, it's only a measurement device.