Blood oxygen level is an important medical tool used to determine how effectively you are taking oxygen into your body. If you're in good health, normal blood oxygen levels almost always fall within a very predictable range. Medical professionals use two primary measurements for determining your blood oxygen level: oxygen saturation and arterial oxygen. The normal values differ for these measurements.
Blood Oxygen Saturation
When you take a breath, oxygen enters your lungs and attaches to a carrier protein called hemoglobin inside your red blood cells. Those same red blood cells release carbon dioxide into your lungs, which leaves your body when you exhale. Newly oxygenated red blood cells carry oxygen to your body.
A pulse oximeter uses light to measure the oxygen saturation level, the percentage of hemoglobin in your red blood cells carrying oxygen. Normal oxygen saturation levels fall between 95 and 99 percent.
Arterial Blood Oxygen
While a pulse oximeter is the most common device used to determine your blood oxygen level, it is sometimes necessary to analyze blood taken directly from an artery to assess your oxygen level. This measurement is called an arterial blood oxygen. A normal arterial blood oxygen level typically falls between 75 and 100 mmHg. Your blood carbon dioxide level and pH -- a measure of acidity or alkalinity -- are usually measured along with the arterial blood oxygen level.