Oxygen saturation refers to the amount or percentage of hemoglobin in the blood that is bound to oxygen molecules. It is usually measured using a pulse oximeter, a non-invasive medical device that clips onto a finger or other part of the body and uses light to measure the amount of oxygen in the blood.

The normal range for oxygen saturation is typically between 95% and 100%. Values below 90% may indicate hypoxemia, which is a low level of oxygen in the blood. Hypoxemia can cause symptoms such as shortness of breath, confusion, and cyanosis (a bluish discoloration of the skin or mucous membranes). Severe or prolonged hypoxemia can lead to serious health problems and requires prompt medical attention.