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What Oxygen Saturation Levels Mean

Updated April 17, 2017

Oxygen saturation is a measure of the amount of oxygen in a person's red blood cells. When blood passes through the lungs, 95 to 100 per cent of the body's red blood cells bind to or become saturated with oxygen. Normal oxygen saturation levels are between 95 and 100 per cent.

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The body needs oxygen to function properly. Oxygen saturation levels are an indication of whether a person's circulatory system or blood is carrying enough oxygen to all the organs in the body. Normal oxygen saturation levels signify the presence of adequate amounts of oxygen in the body.


Hypoxaemia is a condition where the oxygen content of the blood is low. This condition occurs when a person has low oxygen saturation levels. In this situation, the tissues and organs of the body do not get enough oxygen.


The red blood cells are needed to carry oxygen and maintain a normal oxygen saturation level. Low red blood cell levels, also known as anaemia, lead to low oxygen saturation levels because there is not enough red blood cells for oxygen to bind to.

Carbon Monoxide

Carbon monoxide is a toxic gas that is found in car exhaust fumes. This gas has the ability to knock oxygen off a red blood cell and bind to that cell. Inhalation of this gas decreases the amount of oxygen available in the blood and causes low oxygen saturation levels.


Oxygen saturation level is measured using a pulse oximeter. This device is made of a clip and a detector. The clip is attached to a person's finger and shines a light through it. The light coming through the other side of the finger is measured by the detector for oxygen saturation. The red blood cells that are saturated with oxygen absorb and reflect light differently from those that are not.

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About the Author

Ngozi Oguejiofo

Ngozi Oguejiofo has been writing on a freelance basis since 2009 and most of her writings are focused on health. She is currently a registered nurse. She is interested in teaching, and writes articles focused on student nurses for various online publications.

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