Health Library

Pulse oximeter

A pulse oximeter is a device that checks to see how much oxygen your blood is carrying. It's a fast, simple way to learn this information without using a needle to take a blood sample.

Usually a small clip is put on the end of your finger. (Sometimes it's put on your toe or earlobe.) The device shines a light beam through the skin. It estimates your oxygen level by measuring the percentage of your blood that's carrying oxygen. Your oxygen level (or oxygen saturation, SpO2) shows on the display screen.

Pulse oximeters are used in doctors' offices and hospitals. Your doctor may think it's a good idea for some people to use one at home. This may include people who have a condition that affects their oxygen levels. Examples include people who have long-term heart or lung problems or an infection like COVID-19.