Calculator
Anion Gap Calculator
Calculate the serum anion gap with or without potassium, including the albumin-corrected anion gap.
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Formula & Clinical Notes
Formula
AG = Na − (Cl + HCO₃) · AG with K = (Na + K) − (Cl + HCO₃) · AG corrected = AG + 2.5 × (4 − Albumin)
Clinical Notes
The normal anion gap is approximately 8-12 mEq/L without potassium (12-16 mEq/L with potassium). A high anion gap metabolic acidosis indicates accumulation of unmeasured anions (lactate, ketones, renal failure, toxins). Because albumin is the major unmeasured anion, hypoalbuminemia can mask a high gap; correct the gap by adding 2.5 × (4 − albumin) when albumin is expressed in g/dL.
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