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Anion Gap Calculator

Parameters

Contemporaneous chemistry-panel inputs

Enter sodium, chloride, total CO₂, and albumin from one contemporaneous chemistry panel. Use the local laboratory upper reference limit for anion gap without potassium; 12 mmol/L is an editable equation convention, not a universal normal limit.

RequiredAllowed: 40–205 mmol/L

RequiredAllowed: 50–200 mmol/L

RequiredAllowed: 5–50 mmol/L

RequiredAllowed: 1–80 g/L

RequiredAllowed: 1–30 mmol/L

Clinical context

Clinical scope: adults using sodium, chloride, total CO₂, and albumin from one contemporaneous chemistry panel. Chemistry total CO₂ is distinct from actual HCO₃⁻ calculated by a blood-gas analyzer; do not substitute or mix samples. Formulas: AG = sodium − chloride − total CO₂. Corrected AG = AG + 0.25 × (40 − albumin [g/L]). Delta ratio = (corrected AG − entered local upper reference) / (24 − total CO₂), calculated only when corrected AG is above that reference and total CO₂ is below 24 mmol/L. Observed and corrected AG display to one decimal; comparisons use unrounded values. The 2025 adjunctive delta bands are <0.8, 0.8–1.2 inclusive, and >1.2. Published conventions vary, so these outputs use only possible or compatible language. This tool does not identify etiology or prescribe treatment. Do not use for pediatric, neonatal, or pregnancy-specific interpretation; integrate the patient, local method, specimen handling, lactate, ketones, renal function, and toxicology.