Normal Oxygen Level of a Person

Updated February 21, 2017

Since every person breathes, it might be assumed that all people have the same level of oxygen within their bodies. However, oxygen levels can vary greatly and have a large impact on how a person is able to function. As a consequence, medical professionals have developed standards for the amount of oxygen that should be present within a person's body.

Normal Range

For most people, an oxygen level of 95 per cent to 100 per cent is considered normal. Within this range, the cells of the body have enough oxygen to carry out necessary functions and an individual feels alert and energised. A level outside of the 95-to-100-percent range is cause for concern and warrants examination or testing by a medical professional. This is true regardless of whether the oxygen is higher or lower than the optimal range.


The level of oxygen in the body can be measured in multiple ways. The most common way is through a blood test. This test, known as an arterial blood gases (ABG) test, is done through a traditional blood draw. Another means of testing oxygen levels is with a pulse oximeter. This method measures oxygen levels with a light sensor.

Low Oxygen Level Problems

If the level of oxygen in an individual's body is too low, mild to severe complications can occur. The person may experience fatigue and have a greyish blue skin hue. The primary symptom of low oxygen, however, is shortness of breath. This may be accompanied by dizziness, fainting or disorientation.

High Oxygen Level Problems

High oxygen levels are just as much of a concern as low oxygen levels. The main issue with an oxygen level that is too high is that it signals the brain to tell an individual's body that it doesn't need to breathe. For this reason, medical professionals have associated high oxygen levels with medical conditions such as sleep apnoea, in which an individual periodically stops breathing as they sleep.

Environmental & Biological Factors

The level of oxygen in a person's body is affected by both environmental and biological factors. For instance, if a person lives in an area where air pollution is high, he may have lower oxygen levels because there is less oxygen in the air that he breathes. Athletes tend to have higher oxygen levels because they are able to train their bodies to maximise the efficiency of every inhalation.


Abnormal oxygen levels can be treated with oxygen therapy. Sometimes this involves wearing an oxygen mask, spending time in an oxygen chamber or receiving peroxide injections (this is controversial and is more dangerous). Obtaining higher oxygen levels via these means may decrease the risk of cancer due, according to Nobel laureate Dr. Otto Warburg, who found that cancer cells cannot thrive in a high-oxygen environment. It also may improve general health, since many pathogens, like cancer cells, require non-aerobic conditions. Oxygen therapy should not be seen as a substitute for other medical treatments or therapies such as antibiotics, and it should be carried out under medical supervision.

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About the Author

Wanda Thibodeaux is a freelance writer and editor based in Eagan, Minn. She has been published in both print and Web publications and has written on everything from fly fishing to parenting. She currently works through her business website,, which functions globally and welcomes new clients.