Anion Gap Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026
Disclaimer: This calculator is provided for informational and educational purposes only and does not constitute financial, medical, legal, or other professional advice. Always consult a qualified professional before making decisions based on these results.
The first step in evaluating metabolic acidosis
The anion gap represents unmeasured anions in the blood, calculated from routinely measured electrolytes - it is a standard first step clinicians use to help classify the underlying cause of metabolic acidosis.
Worked example
For sodium 140, chloride 104, and bicarbonate 24 mEq/L:
AG = 140 - (104 + 24) = 12.0 mEq/L (Within typical reference range)
| Anion Gap | General Interpretation |
|---|---|
| 8-12 mEq/L | Typical reference range |
| Above 12 mEq/L | May suggest an elevated anion gap metabolic acidosis |
An elevated gap points toward causes like ketoacidosis, lactic acidosis, renal failure, or certain toxic ingestions, while a normal-gap acidosis suggests different causes like diarrhea or renal tubular acidosis. This is an informational tool only, not a substitute for clinical judgment - lab reference ranges vary by laboratory, and results must always be interpreted by a qualified healthcare provider.