HomeHealth articlesoxygen saturationWhat Is Oxygen Saturation?

Oxygen Saturation: An Overview

Verified dataVerified data

4 min read


The amount of oxygen circulating with the red blood cells is measured by the blood oxygen level. The article below discusses oxygen saturation in detail.

Medically reviewed by

Dr. Muhammad Zohaib Siddiq

Published At December 18, 2023
Reviewed AtApril 13, 2024

What Is Blood Oxygen Level?

Individuals probably did not give their blood oxygen levels much thought prior to the year 2020. Perhaps when they were ill or had surgery, a medical expert attached a sensor to their fingertip to measure the levels, and they probably have not given those metrics much thought since then. Up until now, that is. Individuals now understand the link between oxygen levels and lung function thanks to COVID-19 (coronavirus of 2019). And some of the most recent fitness tracker manufacturers include capabilities that can assess blood oxygen levels.

The amount of oxygen transported by the red blood cells in the blood is measured by the blood oxygen level. The blood oxygen level is tightly controlled by the body. Human health depends on maintaining the proper balance of oxygen-saturated blood. The majority of children and adults do not require blood oxygen monitoring. In fact, many medical professionals would not check it unless someone exhibits symptoms of a condition, like chest pain or difficulty breathing. However, those who have ongoing medical issues might need to keep an eye on their blood oxygen levels. Asthma, cardiac conditions, and chronic obstructive pulmonary disease (COPD) are among them. In these circumstances, keeping an eye on the blood oxygen level might help doctors decide whether or not current therapies are effective and if they need to be changed.

How Does the Blood Become Oxygenated?

Starting with the alveoli, or air sacs, people can better comprehend how blood is enriched with oxygen. The lungs contain millions of these tiny air sacs. They perform a crucial task by transferring molecules of oxygen and carbon dioxide into and out of the bloodstream. Hemoglobin, a component of the blood, binds to oxygen molecules as they travel through the alveoli. Oxygen effectively tags along and is dropped off at the tissues of the body as the hemoglobin circulates. This allows the cycle to restart because hemoglobin transfers carbon dioxide from the tissues back to the alveoli.

The blood's level of oxygen is influenced by a number of important factors, including:

  • How much oxygen is consumed?

  • How efficiently do the alveoli exchange carbon dioxide for oxygen?

  • What percentage of hemoglobin is contained in red blood cells?

  • How effectively does hemoglobin draw oxygen?

Hemoglobin typically has sufficient oxygen to suit the body's requirements. However, some disorders make it less competent to bind to oxygen.

How Is Our Oxygen Saturation Level Measured?

The two most common methods for determining oxygen saturation are pulse oximetry (SpO2) and the arterial blood gas test (ABG or SaO2). While pulse oximetry can be performed in a variety of healthcare facilities, including the healthcare provider's office, ABG is often only performed in a hospital setting.

  • Arterial Blood Gas

The extent of carbon dioxide and oxygen in the blood coursing through the veins is known as an arterial blood gas value. Blood is drawn from an artery, such as the radial artery in the wrist or the femoral artery in the groin, by a nurse or laboratory technician. The sample is evaluated right away in a laboratory or by a machine. The healthcare professional can gain insight into the hemoglobin's ability to exchange oxygen and carbon dioxide by looking at the arterial blood gas value.

  • Pulse Oximetry

A pulse oximetry reading indicates the percentage of oxygen present in arterial blood. Pulse oximetry, in contrast to the ABG test, is non-invasive. Many types of pulse oximeters are available that can be purchased online. A sensor is used in the test to read the blood's reflected wavelengths. Simply secure the pulse oximeter probe to the finger, earlobe, or other body parts. Results are displayed on a screen shortly after. Wearable pulse oximetry devices can be used to check a person's oxygen saturation levels; certain watches even offer this capability. Pulse oximetry equipment can be purchased online or at a neighborhood pharmacy.

What Is a Healthy Blood Oxygen Level?

The oxygen saturation level is a measurement of the blood oxygen level. When utilizing a blood gas, it may be referred to as a PaO2 and an O2 sat (SpO2) when using a pulse oximeter.

1. Normal Blood Oxygen Level:

For healthy lungs, a normal ABG (arterial blood gas) oxygen level ranges from 80 to 100 millimeters of mercury (mm Hg). The blood oxygen level (SpO2) should be between 95 and 100 percent if one had a pulse oximeter test. In cases of COPD (chronic obstructive pulmonary disease) or similar lung disorders, these values may not apply, though. People with severe COPD, for instance, frequently keep their pulse oxygen levels (SpO2) between 88 and 92 percent.

2. Low Blood Oxygen Level:

Hypoxemia is a condition where a blood oxygen level is below normal. Frequently, hypoxemia is a cause for concern. The severity of hypoxemia increases with decreasing oxygen levels. Tissues and organs of the body may face complications as a result of this. A PaO2 value under 80 mm Hg or a pulse oxygen saturation (SpO2) below 95 percent is typically regarded as low. Knowing what is typical for someone is crucial, particularly if they have a long-term lung problem.

3. High Blood Oxygen Level:

It is challenging to have excessively high oxygen levels when breathing naturally. The majority of the time, those who utilize supplemental oxygen experience high oxygen levels. On arterial blood gas, this can be seen.

What Causes a Low Blood Oxygen Saturation Level?

The blood oxygen level may be adversely affected by the following circumstances:

  • Emphysema (a lung condition characterized by shortness of breath and coughing).

  • Syndrome of acute respiratory distress.

  • Lung collapse.

  • Anemia.

  • Asthma.

  • Congenital heart conditions.

  • Pulmonary embolism.

These ailments may make it difficult for the lungs to properly take in oxygen-rich air and expel carbon dioxide similar to how blood illnesses and circulatory system issues can impede the blood from absorbing oxygen and carrying it throughout the body. Oxygen saturation levels may decrease as a result of any one of these issues or illnesses. One can start to experience the signs and symptoms of hypoxemia when their oxygen levels drop.


Most people do not need to check their blood oxygen levels on a frequent basis. Typically, only those with medical conditions that result in low oxygen levels are asked to check their oxygen levels. Monitoring oxygen saturation on a frequent basis is crucial for those with long-term diseases that impact their lungs, blood, or circulation. Remember that an oxygen saturation level below 95 percent is typically abnormal and necessitates immediate medical intervention. A decrease in oxygen saturation will cause cell and tissue death if not attended to quickly.

Source Article IclonSourcesSource Article Arrow
Dr. Muhammad Zohaib Siddiq
Dr. Muhammad Zohaib Siddiq



oxygen saturation
Community Banner Mobile
By subscribing, I agree to iCliniq's Terms & Privacy Policy.

Source Article ArrowMost popular articles

Do you have a question on

oxygen saturation

Ask a doctor online

*guaranteed answer within 4 hours

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website. Read our Editorial Process to know how we create content for health articles and queries.

This website uses cookies to ensure you get the best experience on our website. iCliniq privacy policy