Blood Oxygen Level Chart and Information

Author: Ian C. Langtree
Published: 2022/09/01 - Updated: 2024/04/07
Publication Type: Informative
Contents: Summary - Main - Related Publications

Synopsis: Chart illustrates typical and diminished blood oxygen saturation levels, along with guidance on measuring sO2 levels, and causes and symptoms of diminished blood oxygen. Oxygen saturation (sO2) refers to the percentage amount of oxygen in the blood. Among other things, it provides information about the functional capacity of the lungs and the effectiveness of oxygen transport in the blood. Oxygen saturation can be determined either outside the body via pulse oximetry or invasively with the aid of a blood gas analysis.

Blood Oxygen Saturation

Oxygen is carried around in your red blood cells by a molecule called haemoglobin. In medicine, oxygen saturation, commonly referred to as "sats", measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen. Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal arterial blood oxygen saturation levels in humans are 97-100 percent. If the level is below 90 percent, it is considered low and called hypoxemia. Arterial blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed.

Main Digest

When you breathe, oxygen goes through your lungs and enters your bloodstream. The amount of oxygen in your blood is called your blood oxygen level (blood oxygen saturation). Your body needs a certain amount of oxygen to function correctly. Low blood oxygen levels can lead to severe health conditions. Your blood oxygen level is the percentage of the amount of oxygen circulating in your blood.

Measuring Blood Oxygen Level

Pulse Oximeter

A pulse oximeter is a small device that clips onto a finger, an earlobe, or an infant's foot and uses light beams to estimate the oxygen saturation of the blood (how much oxygen is in the blood) and the pulse rate. Oxygen saturation gives information about the amount of oxygen carried in the blood. The pulse oximeter can estimate the amount of oxygen in the blood without drawing a blood sample. They are used often in hospitals and clinics and can also be bought to use at home.

Using a Pulse Oximeter:

NOTE: Several factors can affect the accuracy of a pulse oximeter reading, such as poor circulation, skin pigmentation, skin thickness, skin temperature, current tobacco use, and fingernail polish. To get the best reading from a pulse oximeter:

Continued below image.
Image of a Pulse Oximeter on a person's finger showing Blood Oxygen Level (SpO2) of 97% and pulse rate (PR) of 92 beats per minute.
Image of a Pulse Oximeter on a person's finger showing Blood Oxygen Level (SpO2) of 97% and pulse rate (PR) of 92 beats per minute.

Smart Watches

Some smartwatches can measure your blood oxygen saturation level. For example, in the Apple Watch Series 6 and above, the optical heart sensor has also been redesigned to add blood oxygen measurement capabilities. During a blood oxygen measurement, the back crystal shines red and green LEDs and infrared light onto your wrist. Photodiodes then measure the amount of light reflected. Algorithms use this data to calculate the color of your blood. The color determines your blood oxygen level - bright red blood has more oxygen, while dark red blood has less.

Other Blood Oxygen Level Test Methods

A full Blood Oxygen Level Test will measure:

Blood Oxygen Level Chart

Healthy individuals at sea level usually exhibit oxygen saturation values between 96% and 99% and should be above 94%. At 1,600 meters' altitude (about one mile high), oxygen saturation should be above 92%. Most people have 95 - 100% blood oxygen level. However, some people live normal lives with blood oxygen levels below 95%. Slightly lower values while sleeping are expected, and some users might experience values below 95%. Some people with chronic lung disease or sleep apnea can have normal levels of around 90%.

Blood Oxygen Level Chart
95-100% Average for the population, The red blood cells are well oxygenated and sufficiently transport oxygen around the body.
91 - 94% Below average for the population. Monitor closely.
90% or Less Consider consulting your doctor.

Symptoms of Low Blood Oxygen Level

NOTE: Some patients with low oxygen levels may not show any or all of these symptoms.

Causes of Low Blood Oxygen Level Reading

Blood oxygen levels can get low due to low air oxygen levels as atmospheric oxygen becomes extremely low at high altitudes such as mountainous regions. Decreased capacity of the body to take in oxygen can be caused by lung conditions that include:

If Your Blood Oxygen Levels is Low

Oxygen levels may be low if someone feels short of breath, is breathing faster than usual, or feels too sick to do their usual daily activities; even if a pulse oximeter says their oxygen levels are normal, it may mean you:

These conditions can also be signs of a lung or kidney disease. A blood oxygen level test can't diagnose specific diseases, but your health care provider will order more tests to confirm or rule out a diagnosis if your results are not normal. If you have questions about your results, talk to your doctor or health care provider.

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Cite This Page (APA): Langtree, I. C. (2022, September 1). Blood Oxygen Level Chart and Information. Disabled World. Retrieved April 15, 2024 from

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