How? A blood test can determine blood oxygen saturation level and is a measure of the percentage of your red blood cells that are "saturated" with oxygen. At sea level, about 95%-100% of red cells are "saturated" with oxygen. Levels lower than about 95% may be considered low and may need to be evaluated
Pulse oximetry is a non-invasive method allowing the monitoring of the oxygenation of a patient's hemoglobin.