Anion Gap

Anion Gap is a calculated value representing the difference between measured cations (Sodium, sometimes Potassium) and measured anions (Chloride, Bicarbonate) in the serum. It helps identify the cause of metabolic acidosis. An elevated anion gap suggests acidosis due to accumulation of unmeasured anions (e.g., ketones in DKA, lactate in lactic acidosis, toxins like methanol/ethylene glycol, advanced kidney failure). A normal anion gap acidosis has other causes (e.g., diarrhea, renal tubular acidosis). Albumin level affects the normal range (lower albumin = lower normal AG).