What is normal oxygen saturation?

Normal oxygen saturation refers to the percentage of oxygenated hemoglobin (HbO2) in the blood. In a healthy adult, oxygen saturation levels are typically between 95% and 100%. If the oxygen saturation level falls below 90%, it can indicate a problem with the respiratory or circulatory system. Factors that can affect oxygen saturation levels include altitude, lung and heart diseases, smoking, and anemia. Measuring oxygen saturation is typically done using a pulse oximeter, a non-invasive medical device that clips onto a finger or earlobe to quickly and easily get a reading.