Anion Gap Calculator

How it is calculated

Anion gap = sodium − (chloride + bicarbonate).

What your result means

• Ranges depend on the analyzer: older methods gave about 8 to 16 mEq/L, newer ones about 3 to 9 mEq/L, so use your lab's printed range.
• Some calculations add potassium, which raises the result by the potassium value.
• Your own lab's printed range and your clinician's read of your history come first; this calculator is educational and is not a diagnosis.

Test the inputs

The Metabolic and insulin panel measures the values this calculator uses. Related: sodium, chloride, co2.

Common questions

What is the anion gap formula?

Sodium minus the sum of chloride and bicarbonate. Some labs include potassium with sodium.

Why do anion gap ranges differ between labs?

Typical values shifted lower as laboratory analyzer methods changed, so each lab sets a range for its own equipment.

Is CO2 the same as bicarbonate here?

On a metabolic panel, total CO2 is mostly bicarbonate and is the value used in the calculation.

References

1. Evaluating a low anion gap: A practical approach. Cleve Clin J Med, 2023.
2. Understanding Acid-Base Disorders. Ulster Med J, 2017.