Anion Gap Calculator
Serum anion gap for acid-base interpretation
Equation & limitations
- Equation
- Anion gap = Na − (Cl + HCO₃)
- Version
- Standard definition (no correction for albumin applied here)
- Source
- Defined by Pharmapedia for this tool; standard clinical-chemistry definition.
- Appropriate in
- Adults having serum electrolytes measured for acid-base assessment.
- Limitations
- This is the un-corrected gap. Hypoalbuminaemia lowers the gap, and an albumin-corrected gap is often more informative.
- An abnormal gap is a clue to an acid-base disorder, not a diagnosis — interpretation is clinical.
- Units are mEq/L; the same number is numerically equal in mmol/L.
For educational use. Results support, and do not replace, clinical judgement — check them against the patient and local guidelines.