How to Measure Oxygen Level in the Body

Updated July 20, 2017

The colour of the haemoglobin in your blood changes depending on how much oxygen it is carrying. If it is depleted of oxygen it turns dark red or purple. When it is rich with oxygen it is bright red. A pulse oximeter uses a light source and a light sensor to determine the amount of oxygen that is in your bloodstream. The pulse oximeter shines a light through your fingertip or ear lobe and the sensor that is on the other side of your finger or ear lobe provides a signal that is used to calculate your blood oxygen level.

Connect the sensor clip to the pulse oximeter control box.

Plug the pulse oximeter control box into an electrical socket.

Wash your hands to remove any dirt, blood and any other matter that might impede transmittance of light. Remove any fingernail polish that you might be wearing.

Clip the sensor onto your index finger.

Turn on the pulse oximeter.

Read the oxygen level in your blood on the display. The amount of oxygen in your blood is an indicator of the amount of oxygen in your body.


Don’t self-diagnose of self-treat yourself based on your blood oxygen level. Always consult a licensed physician. Pulse oximeters can be affected by bright light in the vicinity of the sensor.

Things You'll Need

  • Pulse oximeter
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