Blood Anion Gap Test

Anionic gap is a laboratory measurement (not a direct analysis) of the gap between measured positive ions (cations) and measured negative ions (anions) in blood serum. It is usually calculated using the formula: (sodium + potassium) - (chloride + bicarbonate). A normal anionic gap (8–16 mEq/L) reflects the presence of normal, unmeasured anions (such as proteins and phosphates). An elevated gap indicates an accumulation of abnormal acids (such as lactate, ketones, toxins) in the blood, as in metabolic acidosis with a high anionic gap.