About this Anion Gap
The Anion Gap is a calculated value used to identify the cause of metabolic acidosis. It represents unmeasured anions in the plasma, such as albumin, phosphate, sulfates, and organic acids like lactate or ketones.
Who this calculator is for
- Clinicians, trainees, and students reviewing electrolyte panels in acid-base cases.
- People trying to understand why a lab report mentions a high or low anion gap.
- Anyone learning how sodium, chloride, and bicarbonate relate in metabolic acidosis screening.
When to use it
- Use this calculator when BMP or CMP results are available and you want the standard anion gap quickly.
- Use it to compare how the gap changes across repeat electrolyte panels over time.
- Use it as a teaching aid when discussing high-gap versus normal-gap metabolic acidosis.
How to use this calculator
- Enter the Sodium (Na+) level from the basic metabolic panel (BMP).
- Enter the Chloride (Cl-) level.
- Enter the Bicarbonate (HCO3- or CO2) level.
- Check the result to see if the gap is High, Normal, or Low.
Key assumptions
- This uses the standard formula without potassium, which matches many modern lab references.
- The output assumes albumin is not severely abnormal; hypoalbuminemia can lower the measured gap.
- Anion gap is only one part of acid-base interpretation and does not diagnose the cause by itself.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
Key Features
- Standard formula (without Potassium)
- Interpretation guide
- Instant electrolyte analysis
Things to Keep in Mind
This calculator uses the standard formula which assumes normal albumin levels. In patients with significant hypoalbuminemia, the corrected anion gap should be used.