How are Haemoglobin levels measured?

Haemoglobin absorbs light

  • Haemoglobin which is high in O2  and Haemoglobin which is low in O2 will absorb different wave lengths of light. A pulse oximeter is used to measure haemoglobin in small capillaries. It can be placed on a finger, ear lobe or toe.
  • Measurements should be taken when the patient is not moving, wearing nail varnish or has been diagnosed as Hypovolemic (decreased blood volume).
  • People who have been exposed to carbon monoxide poisoning may give a false  positive result.
  • People with very cold hands from conditions such as Reynaud’s syndrome may give an inaccurately low reading.