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Blood Oxygen Levels: Normal and Low – What you Need to Know

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The amount of oxygen circulating in the blood is known as blood oxygen level. Red blood cells carry oxygen gathered from the lungs and transfer it to the entire body. The blood oxygen level in a person’s blood is a measure of how well the body transports oxygen from the lungs to the cells, and it’s vital for their health.

The body closely controls blood oxygen levels to ensure that they remain within a specific range, ensuring that each cell receives enough oxygen. Blood oxygen levels in healthy people range between 75 and 100 millimetres of mercury (mm Hg). The medical profession deems it low when arterial blood gas (ABG) test results reveal an oxygen level below 60 mm Hg. People who have these results may require oxygen supplementation in some situations.

When the body has trouble supplying oxygen to all of its cells, tissues, and organs, a condition called hypoxemia occurs. Hypoxemia is a condition in which a person’s blood oxygen level is abnormally low compared to the usual level of a healthy individual.

Where should your blood oxygen level fall?

The oxygen saturation level is a measurement of the amount of oxygen in your blood. When utilizing a blood gas, it’s referred to as a PaO2 and when using a pulse ox, it’s referred to as an O2 sat (SpO2). These suggestions will assist you in interpreting your results.

Oxygen saturation

The percentage of oxygen in a person’s blood is referred to as oxygen saturation. A pulse oximeter is a gadget that medical practitioners frequently use for either a rapid test or continuous monitoring. The device is small enough to be attached to a person’s fingertip. 

Between 95 and 100 percent oxygen saturation is considered healthy. If a person’s levels go below this range, they may feel symptoms including problems breathing and confusion, which are signs of a shortage of oxygen.

  • Normal For healthy lungs, a normal ABG oxygen level is between 80 and 100 millimeters of mercury (mm Hg). If your blood oxygen level (SpO2) was measured using a pulse oximeter, a normal reading would be between 95 and 100 percent. The medical condition, where the blood oxygen level of an individual is less than average, is also referred to as hypoxemia. During hypoxemia, the body has difficulty delivering oxygen to the organs and tissues.
  • Below normalHypoxemia is defined as a blood oxygen level that is lower than usual. Hypoxia is a common source of worry. Hypoxemia is more severe when oxygen levels are low. This can cause problems with body tissue and organs.
  • Above normal It’s impossible for your oxygen levels to become too high if you’re breathing naturally. People who utilize supplementary oxygen are more likely to have high oxygen levels. On an ABG, this can be seen.

How is your blood oxygen level measured?

Blood oxygen levels can be measured with two tests:

Arterial blood gas 

A blood test is an arterial blood gas (ABG) test. It monitors the amount of oxygen in your blood. It can also detect the presence of various gases in your bloodstream, as well as the pH (acid/base balance). An ABG is quite accurate, but it is also exceedingly invasive.

Your doctor will take blood from an artery rather than a vein to measure your ABG. Because it is easily sensed compared to others in your body, the artery in your wrist is utilized. Because the wrist is a sensitive location, a blood draw there is more unpleasant than one near the elbow. The fact that arteries are deeper than veins add to discomfort.

Pulse oximeter

A pulse oximeter (also known as a pulse ox) is a noninvasive device that measures the quantity of oxygen in your blood. Infrared light is sent into capillaries in your finger, toe, or earlobe to accomplish this. Then it calculates the amount of light reflected by the gases.

The SpO2 level is a measurement that shows what percentage of your blood is saturated. The error window for this test is 2%. As a result, the value could be up to 2% higher or lower than your actual blood oxygen level.

What happens if your oxygen level is too low?

Your body may not function correctly if your blood oxygen levels are too low. To keep your cells healthy, blood transports oxygen throughout your body. Hypoxemia can result in minor symptoms like headaches and shortness of breath. It can impair heart and brain function in extreme situations.

What happens when the oxygen level drops to 70?

When your oxygen level drops to 70, you will experience headaches and dizziness apart from breathlessness. You must consult with your doctor if you observe any of these symptoms so that you can be put on supplemental oxygen to raise the oxygen saturation of the blood.

What happens when the oxygen level drops to 80?

For someone with moderate to severe COPD, anything between 92 and 88 percent is considered safe and average. When it drops below 88 percent, it’s time to go to the hospital, and when it drops to 84 percent or below, it’s time to go to the hospital. It’s harmful for your key organs if you’re below 80%, so you should get help immediately away.

What causes blood oxygen levels to be low?

Lower blood oxygen levels or hypoxemia, a condition where the blood transports very little oxygen to other parts of the body, occurs for various reasons like:

  • A general lack of oxygen in the air.
  • Anemia
  • Collapsed lung
  • Heart diseases
  • Difficulty breathing, thereby preventing the lungs from inhaling and circulating oxygen
  • Reduced ability of the bloodstream to circulate the oxygen to the lungs.

It is also due to the less intake of oxygen while breathing. This medical condition is a cause for concern and can lead to various complications within the body.

Conditions that can lead to hypoxemia

Hypoxemia is a condition in which a person’s blood oxygen level is abnormally low compared to the usual level of a healthy individual. When the body has trouble supplying oxygen to all of its cells, tissues, and organs, this occurs.

How to adjust your blood oxygen level?

You may need to increase your oxygen saturation if your blood oxygen level is too low. This is frequently done with the use of supplementary oxygen. Home supplemental oxygen is a drug that requires a prescription from your doctor. To minimise difficulties, it’s critical to follow your doctor’s exact instructions on how to use home oxygen. It’s possible that your health insurance will pay the cost.

When to See the Doctor

You must identify the symptoms of low blood oxygen levels and seek immediate help to prevent further health complications. It is necessary to identify these symptoms and consult the doctor for proper treatment to restore the blood oxygen levels. You can experience sudden shortness of breath during rest or exercise, or you may even wake up suddenly with shortness of breath.

COVID-19 and Blood Oxygen Levels

In the current COVID-19 pandemic situations, where lung damage may lead to lower blood oxygen levels, monitoring the oxygen levels is an essential part of the treatment and recovery. In many cases, you may experience a decrease in oxygen levels even if you may not display the usual symptoms of COVID-19.


The oxygen saturation helps quantitate the amount of oxygen present in the blood. A reduction in this amount below the normal range causes many complications and requires immediate treatment.

Frequently Asked Questions (FAQs)

What is Blood Oxygen Test and How Should I Prepare Myself

It depends on the type of test being performed. If you are undergoing the ABG test, which requires blood to be drawn from the wrist, your doctor will perform a circulation test before taking the sample. If you are testing the blood saturation at home using the oximeter, you would not require any prior preparation except for a clean fingertip upon which the oximeter will be placed.

What is proning, and how is it useful? 

Proning is a procedure where the patient is made to lie with their face down, that is, on their abdomen. When resting in this position, the oxygenation in the patient improves as the alveolar units remain open. This can be performed up to ten times during the day.

Should I monitor my oxygen levels?

Yes, of course. It is necessary to closely monitor the blood oxygen saturation at home, especially if you are suffering from COVID-19 or any other illness and are continuing to stay home. Post proning practice, you can regularly monitor the SpO2 levels for any change and go to hospital accordingly if your health deteriorates.



Verified By Dr Amitav Mohanty
MBBS, MD -Medicine, Senior Consultant - General Medicine, Apollo Hospitals Bhubanswar
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