SpO2 stands for oxygen saturation and is a measure of how much oxygen your blood is carrying as a percentage of the maximum it could carry. It is represented as arterial oxygen saturation (SaO2) and is measured using a pulse oximeter, which is a small clip that is usually placed on your finger or toe. The oximeter reading indicates what percentage of your blood is saturated with oxygen, as well as your heart rate. For a healthy individual, the normal SpO2 should be between 96% to 99%.

The body needs a certain level of oxygen in the blood to function efficiently, and very low levels of SpO2 can result in serious symptoms. Hypoxemia is a condition where there are low levels of oxygen in the blood, and it can turn into hypoxia, which is low levels of oxygen in the tissue. The most important way that the body maintains healthy SpO2 levels is through breathing, where the lungs take inhaled oxygen and bind it to hemoglobin that then travels throughout the body with the payload of oxygen.