Anion Gap Calculator
Calculate the anion gap from serum sodium, chloride, and bicarbonate to assess metabolic acidosis.
How to Use the Anion Gap Calculator
- Enter serum sodium (Na⁺) in mEq/L.
- Enter serum chloride (Cl⁻) in mEq/L.
- Enter serum bicarbonate (HCO₃⁻) in mEq/L.
- Click Calculate to see the anion gap and interpretation.
Use Cases
- •Evaluating unexplained metabolic acidosis in emergency settings.
- •Monitoring patients with diabetic ketoacidosis or lactic acidosis.
- •Teaching acid-base physiology in medical education.
Formula
Formula: Anion Gap (mEq/L) = Na⁺ − (Cl⁻ + HCO₃⁻). Normal range: 8–12 mEq/L.
Frequently Asked Questions
What is the anion gap used for?
The anion gap helps classify metabolic acidosis. An elevated AG (> 12 mEq/L) suggests accumulation of unmeasured anions such as lactate, ketones, salicylate, or uremic acids (MUDPILES mnemonic).
Should albumin be corrected?
Yes — hypoalbuminemia lowers the anion gap by ~2.5 mEq/L per 1 g/dL decrease in albumin. Use the corrected anion gap formula: AG + 2.5 × (4 − albumin) in patients with low albumin.
Disclaimer
For educational purposes only. Not a substitute for clinical judgment. Anion gap must be interpreted alongside pH, PCO2, bicarbonate, and clinical context.