Anion Gap Calculator

Calculate anion gap and corrected anion gap for metabolic acidosis workup. Includes delta ratio interpretation.

Electrolytes

Sodium (Na⁺)

mEq/L

Serum sodium. Normal: 135-145 mEq/L. The main measured cation in the anion gap calculation. Also check for pseudohyponatremia in hyperlipidemia/hyperproteinemia.

Chloride (Cl⁻)

mEq/L

Serum chloride. Normal: 98-106 mEq/L. One of the measured anions. Elevated in non-anion gap metabolic acidosis (NAGMA). Decreased in metabolic alkalosis from vomiting.

Bicarbonate (HCO₃⁻)

mEq/L

Serum bicarbonate (can use CO₂ from BMP). Normal: 22-28 mEq/L. Decreased in metabolic acidosis; increased in metabolic alkalosis or respiratory compensation.

Albumin

g/dL

Serum albumin. Normal: 3.5-5.0 g/dL. Essential for correcting anion gap. Low albumin will lower the anion gap, potentially masking a HAGMA.

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Anion Gap

— mEq/L

Enter electrolyte values

Corrected AG

—

Adjusted for albumin

Delta Gap

—

Excess above 12

Status

Low

The Formulas

Anion Gap

AG = Na⁺ - (Cl⁻ + HCO₃⁻)

= 140 - (104 + 24) = mEq/L

Corrected AG (for albumin)

Corrected AG = AG + 2.5 × (4 - Albumin)

= + 2.5 × (4 - 4) = mEq/L

Frequently Asked Questions