Anion Gap Calculator
The anion gap is a key lab value used to evaluate metabolic acidosis. Enter your sodium, chloride, and bicarbonate values to calculate the anion gap, and optionally add albumin for a corrected result.
The anion gap is calculated as: AG = Na+ - (Cl- + HCO3-). The normal range is 8-12 mEq/L. An elevated anion gap (above 12) suggests the presence of unmeasured anions, which points toward anion gap metabolic acidosis.
The classic mnemonic for elevated anion gap causes is MUDPILES: Methanol, Uremia, Diabetic ketoacidosis, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, and Salicylates.
Albumin correction is important because albumin is a major unmeasured anion. Low albumin (common in hospitalized patients) artificially lowers the anion gap, potentially masking a true anion gap acidosis. The correction formula adds 2.5 mEq/L for every 1 g/dL that albumin is below 4.0. For example, if a patient has an AG of 10 but albumin of 2.0, the corrected AG is 10 + 2.5 x (4.0 - 2.0) = 15 mEq/L, revealing an elevated gap.
The delta-delta ratio helps identify mixed acid-base disorders when the AG is elevated. A ratio below 1 suggests an additional non-AG acidosis, 1-2 indicates a pure AGMA, and above 2 suggests a concurrent metabolic alkalosis.
Disclaimer: This calculator is for educational reference only. Always interpret lab values in the full clinical context. Do not use this tool as a substitute for professional medical judgment.