A calculation based on measurements in serum or plasma to assist with determining the cause of a metabolic acidosis of unknown origin.


Anion Gap = Sodium + Potassium – (chloride + bicarbonate) (all measurements in mmol/L)


Note: variability in result due to uncertainty in measurements approx. +/- 5 mmol/L.


For more information, see the SydPath Information Page

Sodium range is 80-190 mmol/L
Potassium range is 1.0-12.0 mmol/L
Chloride range is 60-140 mmol/L
Bicarbonate range is 0-50 mmol/L
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Anion Gap


Reference Interval : 10 - 18 mmol/L Interpretation The more common causes of a raised anion gap are as follows: • Elevated serum lactate • Ketoacidosis (raised beta-hydroxybutyrate and acetoacetate) • Reduced kidney function • Toxins (e.g. ethanol, methanol, ethylene glycol, salicylates)