Oxygen saturation

relative measure of the amount of oxygen that is dissolved or carried in a given medium

Oxygen saturation or dissolved oxygen (DO) is a relative measure of the amount of oxygen (as O2) that is dissolved in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor. Or it can be measured with an optode in liquid media, usually water. The standard unit is milligrams per litre (mg/l) or parts per million (ppm). Fish, invertebrates, plants, and aerobic bacteria all require oxygen (dissolved in water) for respiration.[1] In medicine, oxygen saturation refers to oxygenation. This means when oxygen molecules (O
) enter the tissues of the body.


  1. Ecology and Classification of North American Freshwater Invertebrates, eds. James H. Thorp; Alan P. Covich (Amsterdam; Boston: Academic Press, 2010), p. 32