HomeHealth A-ZAll You Wanted to Know About Blood Oxygen Levels

All You Wanted to Know About Blood Oxygen Levels

What are Blood Oxygen Levels?

The amount of oxygen in the blood circulating in the body is called the blood oxygen level. The oxygen in the blood is carried by a specific type of cell called the Red Blood Cells (RBCs) that transport the oxygen from the lungs to different body parts. As we know, oxygen is an essential element for the proper functioning of our organs. Thus, the quantitative value of the person’s oxygen levels determines the lung function and the distribution in the body.

Blood oxygen levels are measured in two ways.

Arterial Blood Gas (ABG)

Arterial blood gas (ABG) is a blood test that measures the oxygen level in your blood. It can detect the level of other gases in the blood, including the pH (acid/base) level. ABG test is very accurate, but it is invasive.

To get an ABG measurement, blood will be drawn from the artery rather than the vein. Unlike the veins, arteries have a pulse which can be felt. In addition, blood drawn from the arteries is oxygenated while the blood in the veins is not.

The artery in the wrist is used, as it can be felt easily compared to others in our body.

Since the wrist is a sensitive region, drawing blood from there is more uncomfortable compared to the vein near the elbow. Also, arteries are deeper than veins, adding to the discomfort.

Pulse Oximeter (Pulse Ox)

A pulse oximeter or pulse ox is a non-invasive device that measures the amount of oxygen in the blood by sending infrared light into capillaries in your finger, earlobe, or toe. And then it estimates how much light is reflected off the gases.

A reading shows what percentage of the blood is saturated, called SpO2 level. However, this test has a 2% error window, which means the reading can be as much as 2% higher or lower compared to your actual blood oxygen level.

A pulse oximeter test can be slightly less accurate, but very easy for physician to perform. That is why doctors rely on this test for fast readings.

As a pulse oximeter is non-invasive, you can perform this test by yourself. Pulse oximeter devices can be purchased at most stores that carry health-related products or online.

What Should be the Oxygen Level in the Blood?

Your blood oxygen measurement is called oxygen saturation level. In medical language, you may hear it called, SpO2 (O2 sat) when using pulse oximeter and PaOwhile using a blood gas.

Normal: A normal ABG oxygen level for individuals with healthy lungs falls between 80 and 100 mm Hg (millimeters of mercury). If a pulse oximeter measured the blood oxygen level (SpO2), normal reading is typically 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.

What are the Symptoms of Low Blood Oxygen Levels?

Hypoxemia symptoms are as follows : has several symptoms that the body experiences. These are:

  • Headache
  • Restlessness
  • Chest pain
  • Shortness of breath
  • Confusion
  • Lack of coordination
  • Dizziness
  • High blood pressure
  • Rapid beating of the heart

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.

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What are the Causes of Low Blood Oxygen Levels?

Lower blood oxygen levels or hypoxemia, a condition where the blood transports very little oxygen to other parts of the body, occur for various reasons. Low blood oxygen levels can occur due to the following reasons:

  • A general lack of oxygen in the air.
  • Difficulty breathing, thereby preventing the lungs from inhaling and circulating


  • Reduced ability of the bloodstream to circulate the oxygen to the lungs.
  • This 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

What is normal blood oxygen levels?

The normal arterial blood oxygen level is between eighty and a hundred millimeters of mercury. That is between 95% and 100%  SpO2. But if you have a lung disease, your range may vary between 88% and 92%. Even if you are have COVID-19 with lung damage (suffering from acute respiratory illness) your SpO2 levels may drop below 92%, and you may need supplemental oxygen.

Does blood oxygen levels goes above the normal?

It is quite unlikely to have blood oxygen levels above normal and is only observed when your breathing is assisted or put on supplemental oxygen.

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)

Do I need to prepare myself for the blood oxygen test?

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.

How to increase the oxygen levels in the body? What is proning, and how is it useful?

If the oxygen saturation level of the blood drops below ninety-four percent, you can practice proning at home, too, especially if the hospitals near your location have a shortage of beds and space. 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.

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.

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

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