What is SpO2?

Reviewed by Dr. A. Sharma, MD (Pulmonology) · Written by Raymedico Editorial · Editorial policy

SpO2 is an estimate of the oxygen saturation of your blood, measured non-invasively with a pulse oximeter. The "Sp" indicates it is a peripheral measurement; "O2" refers to oxygen.

A reading of 95% or above is considered normal for most healthy adults at sea level. Values below 90% indicate hypoxaemia and require immediate medical attention.

SpO2 is measured using red and infrared light that passes through or reflects off a perfused tissue bed (usually a fingertip or earlobe). Oxyhaemoglobin and deoxyhaemoglobin absorb these wavelengths differently, allowing the sensor to calculate the ratio.