Anion Gap Calculator
Calculate serum anion gap and albumin-corrected anion gap for metabolic acidosis workup, with delta-delta ratio for mixed disturbances.
Results
What is it?
For educational and clinical reference only. Not a substitute for professional medical judgment. Always verify with current clinical guidelines and consult qualified healthcare providers. The anion gap (AG) reflects unmeasured anions in plasma: AG = Na+ - (Cl- + HCO3-). Normal range is 8�12 mEq/L. An elevated AG indicates accumulation of organic acids. The albumin-corrected AG adjusts for hypoalbuminemia (add 2.5 mEq/L per 1 g/dL drop in albumin below 4). Causes of elevated AG acidosis: MUDPILES � Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates.
How to use
Enter the serum sodium, chloride, and bicarbonate values from the basic metabolic panel. Enter the serum albumin (default 4 g/dL). The calculator computes raw AG, albumin-corrected AG, and the delta-delta ratio to screen for mixed acid-base disorders.
Example scenario
Na 140, Cl 100, HCO3 15, Albumin 2.5 g/dL. Raw AG = 140 - 100 - 15 = 25 mEq/L (elevated). Corrected AG = 25 + 2.5�(4-2.5) = 25 + 3.75 = 28.75 mEq/L. Delta ratio = (25-12)/(24-15) = 13/9 = 1.44 (suggests pure AG acidosis with no concurrent metabolic alkalosis).
Pro tip
Always use the albumin-corrected AG in critically ill patients � hypoalbuminemia can mask a true high-AG acidosis. A delta ratio <0.4 suggests normal-AG acidosis co-existing; >2 suggests metabolic alkalosis or chronic respiratory acidosis co-existing. Interpret the AG in the context of the full clinical picture and ABG.