Anion Gap - Normal Value Ranges

Normal Value Ranges

Modern analyzers make use of ion-selective electrodes which give a normal anion gap as <11 mEq/L. Therefore according to the new classification system a high anion gap is anything above 11 mEq/L and a normal anion gap is often defined as being within the prediction interval of 3–11 mEq/L, with an average estimated at 6 mEq/L.

In the past, methods for the measurement of the anion gap consisted of colorimetry for and as well as flame photometry for and . Thus normal reference values ranged from 8 to 16 mEq/L plasma when not including and from 10 to 20 mEq/L plasma when including . Some specific sources use 15 and 8–16 mEq/L.

A reference range provided by the particular lab that performs the testing should be used to determine if the anion gap is outside of the normal range. A certain proportion of normal individuals may have values outside of the 'normal' range provided by any lab.