Blood oxygen levels can also be measured using an instrument known as a pulse oximeter.
Blood oxygen levels can also be measured using an instrument known as a pulse oximeter.

Blood oxygen levels (arterial oxygen) indicate the oxygen levels present in the blood that flows through the arteries of the body.

  • Normal arterial oxygen pressure (PaO2) measured using the arterial blood gas (ABG) test is approximately 75 to 100 millimeters of mercury (75-100 mmHg).
  • When the level goes below 75 mmHg, the condition is generally termed as hypoxemia.
  • Levels under 60 mmHg are considered very low and indicate the need for supplemental oxygen. Supplemental oxygen is provided through an oxygen cylinder that is connected to the nose via a tube, with or without a mask.

What should oxygen levels be?

Blood oxygen levels can also be measured using an instrument known as a pulse oximeter.

  • The normal oxygen levels in a pulse oximeter usually range from 95% to 100%.
  • Blood oxygen levels below 90% are considered low (hypoxemia).

Hyperoxemia is generally detected using ABG testing and is defined as blood oxygen levels above 120 mmHg. This is mostly seen in hospitals when patients are exposed to high pressures of supplemental oxygen for prolonged periods (3 to more than 10 hours).

What causes blood oxygen levels to become low?

Blood oxygen levels can get low due to any of the problems that include:


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How are blood oxygen levels checked using the ABG test?

Blood oxygen levels can be checked by withdrawing blood from your artery present in the wrist, elbow, or groin. You may feel a sharp pain when the needle enters the artery. The blood will be put in an ABG machine (blood gas analyzer) that provides your blood oxygen levels in the form of the partial pressure of oxygen (PaO2).

How are blood oxygen levels checked using a pulse oximeter?

A pulse oximeter is a small, mobile, and handy medical device. It is most commonly used when doctors want to know your blood oxygen levels quickly. It is also used to monitor the response of your body to certain medications or supplemental oxygen. Blood oxygen levels are indicated as SpO2, which is the percent saturation of oxygen in the blood.

The test that measures blood oxygen levels using a pulse oximeter is known as pulse oximetry. The procedure is very simple and requires only clipping the pulse oximeter in between any of the fingers for a few seconds. The reading appears on the pulse oximeter screen. This test may be slightly less accurate than ABG but is easier to perform than ABG tests when needed quickly.

  • The brain gets affected when the SpO2 level falls below 80-85%.
  • Cyanosis develops when the SpO2 level drops below 65%.
  • The normal oxygen levels in a pulse oximeter usually range from 95% to 100%.  Note: Normal levels may vary if you have lung disorders. Your doctor can tell what levels are normal for you.

What are the signs and symptoms of hypoxemia?

Hypoxemia can give rise to many signs and symptoms depending on its severity. These signs and symptoms include:

Not having enough blood oxygen levels results in inadequate oxygen supply to the organs and tissues of the body. Severe hypoxemia can become dangerous. If left untreated for a long time, it can end up affecting the brain or heart.

How is hypoxemia treated?

Treating hypoxemia involves measures that increase the levels of oxygen in the blood. This is achieved by

  • Treating underlying conditions: Treating the cause of hypoxemia is the most important part of the therapy that gives long-lasting effects. Many times, medications are given through an inhaler that quickly enables you to breathe the medicine into your lungs.
  • Oxygen therapy: You are given supplemental oxygen through an oxygen cylinder (which can be portable). The pressure of delivered oxygen can be controlled.

How can you prevent hypoxemia?

You can maintain your normal blood oxygen levels after you recover from hypoxemia.

Here are a few lifestyle steps you can take to help prevent hypoxemia:


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Medically Reviewed on 10/15/2020
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Starr N, et al. Pulse oximetry in low-resource settings during the COVID-19 pandemic. The Lancet Global Health. 2020 Sep 1;8(9):e1121-2.