Case of the Month #44 High Anion Gap Metabolic Acidosis

Published 12/10/2023

How is the anion gap calculated?

Anion gap (AG) is calculated using the equation:

  • AG = sum of major cations - sum of major anions
  • AG = (Na+ + K+) – (Cl- + HCO3-)

Normal AG = 8 to 14 mmol/L. Given serum must display electrochemical neutrality, this gap represents that there are a greater amount of unmeasured anions than unmeasured cations.

Elevation of the AG is indicative of a metabolic acidosis.