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Oximetry is a technology that measures the oxygen level in the blood. This is also known as oxygen saturation level. This measurement is taken with a device called a pulse oximeter. This device also measures the heart rate (pulse). The measurement helps to assess:
  • A person's oxygen level and breathing.
  • The need for or effectiveness of oxygen therapy or other treatments for lung disease.
  • How well a person can tolerate increased activity.

If a more accurate measurement is needed, a blood sample will be taken.

How is an oximetry reading obtained?

  • A tape sensor or clip with a light source and a light detector will be placed on an area of the body.
    • For children and adults, the sensor is usually placed on a finger, with the light centered over the nail bed. The sensor may also be placed on an earlobe or toe.
    • For babies, a tape sensor is usually placed around areas such as the sole of a foot or the palm of a hand.
  • The device will beam light through the skin and blood. This cannot be felt.
  • The levels of light received by the detector will be measured, and the percentage of blood cells carrying oxygen will be determined.

Oximetry may be used continuously or may be used at specified intervals.

Are there any risks associated with oximetry?

The risks associated with oximetry are rare. However, there is a risk of skin breakdown if a sensor is left in the same spot for long periods of time.

What can affect the accuracy of the oximetry reading?

Pulse oximetry depends on the amount of light absorbed as it passes through skin tissue. Because of this, the accuracy of this measurement can be affected by one or more of the following:
  • Factors such as:
    • Dark nail polish or artificial nails.
    • Very dark skin.
    • Shivering or too much movement.
    • Bright, artificial lighting.
    • Long-term, or chronic, smoking and recent breathing-in (inhalation) of smoke or carbon monoxide.
  • Conditions such as:
    • Extreme coolness or poor blood flow to the area where the sensor is placed.
    • Excessive sweating or extreme warmth of the area where the sensor is placed.
    • Anemia, or low levels of hemoglobin or red blood cells.
    • Polycythemia vera. This is a bone marrow disease that causes high levels of red blood cells, white blood cells, and platelets.

What is the meaning of the oximetry reading?

The normal value depends on your medical history and your elevation above sea level.
  • Most healthy people have oxygen saturation levels between 95% and 100%.
  • Low oxygen saturation levels are below 90%. This may happen in people with lung conditions, such as chronic obstructive pulmonary disease (COPD). In this case, supplemental oxygen therapy may be needed.


  • Oximetry uses a small device to measure the oxygen level in the blood.
  • The light in the sensor cannot be felt. The risks associated with oximetry are rare.
  • Most healthy people have oxygen levels between 95% and 100%. A low oxygen saturation level is below 90%.
  • People with low oxygen levels may need supplemental oxygen.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.