Renal & Electrolytes

Anion Gap Calculator

Sodium minus chloride and bicarbonate: sorts a metabolic acidosis into high-gap (lactate, ketones, toxins, renal failure) or normal-gap.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

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Formula

Anion Gap = Na - (Cl + HCO₃)

How it is used

• Normal Anion Gap is typically 8 to 12 mEq/L.
• An elevated gap indicates an unmeasured anion (e.g., MUDPILES: Methanol, Uremia, DKA, Propylene glycol, Iron/INH, Lactic acidosis, Ethylene glycol, Salicylates).

Same formula as the app. Open it in the web app.

Related one-pagers

• ABG Interpretation in 6 StepsAnion gap · About 12 · Lab ranges vary
• CRRT (Continuous Renal Replacement)Citrate accumulation: patient iCa falls despite more calcium, total Ca rises, the total-to-ionized ratio is 2.5 or more (same units), and an anion gap acidosis appears. Report it; protocols cut or stop citrate.
• DKA and HHSDo not use the anion gap or urine ketones to call resolution
• Toxidromes and AntidotesEthylene glycol · Coma, seizures, AKI, anion gap over 27 · AG 23–27; level over 310 mg/dL on fomepizole

Related calculators

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• Corrected Calcium
• Corrected Sodium (Hyperglycemia)
• Creatinine Clearance (Cockcroft-Gault)
• CRRT Effluent Dose (mL/kg/h)
• Fractional Excretion of Sodium (FENa)
• Fractional Excretion of Urea (FEUrea)
• Free Water Deficit

For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.