The anion gap is a method of assessing the contribution of unmeasured anions to acidosis. It is calculated as a difference between the total of sodium and potassium ion concentration, minus the total of chloride and bicarbonate concentration. Some people omit the potassium. Thus:
The normal range for the anion gap is 6 - 16 mmol/l (1). The anion gap provides a measure of the difference between unestimated anions - phosphate, acetate and ketones - and cations.
The anion gap is likely to abnormally high in most conditions of acidosis except:
Note that reference ranges may vary between laboratories.
Reference:
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