Anion Gap Calculator | Formula, Interpretation & Clinical Guide

Anion Gap Calculator

Calculate anion gap using serum sodium, chloride, bicarbonate, and optional potassium. Includes anion gap formula, interpretation, and related laboratory calculations.

Learn more about Anion Gap

Understand the anion gap formula, normal range, high and low anion gap, albumin correction, and metabolic acidosis.

Read the Complete Anion Gap Guide →

Serum Sodium (Na) mmol/L

Serum Chloride (Cl) mmol/L

Serum Bicarbonate (HCO₃) mmol/L

Serum Potassium (K) Optional

Anion Gap Result

Anion Gap -

Calculation Method -

General Interpretation -

Formula Used

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Anion Gap Formula

Without Potassium

AG = Na − (Cl + HCO₃)

With Potassium

AG = (Na + K) − (Cl + HCO₃)

The potassium-excluded equation is commonly used in clinical laboratory practice. Always compare the result with the reference interval used by the performing laboratory.

Anion Gap Calculation Example

Sodium: 140 mmol/L

Chloride: 104 mmol/L

Bicarbonate: 24 mmol/L

AG = 140 − (104 + 24)
AG = 12 mEq/L

What Does the Anion Gap Mean?

The anion gap is a calculated laboratory value used mainly during the evaluation of electrolyte and acid-base disorders. An increased anion gap can occur when unmeasured anions accumulate in plasma.

Albumin is an important unmeasured anion. Therefore, hypoalbuminemia can lower the measured anion gap and should be considered during interpretation.

High Anion Gap

An increased anion gap may occur with conditions such as lactic acidosis, ketoacidosis, kidney dysfunction, and certain toxic exposures.

Anion gap should not be interpreted as an independent diagnostic test. Clinical findings and other laboratory results should also be considered.

Low Anion Gap

A low anion gap may occur with hypoalbuminemia, analytical variation, increased unmeasured cations, some paraproteinemias, or certain measurement interferences.

Anion Gap Formula & Normal Range

Want to understand the calculation in more detail? Read the complete LabProSuite expert guide covering anion gap formula, normal range, high anion gap, low anion gap, albumin correction, and metabolic acidosis.

Read Anion Gap Expert Guide →

Related LabProSuite Calculators

Corrected Anion Gap Calculator Adjust anion gap for serum albumin. Corrected Sodium Calculator Calculate sodium corrected for glucose. Corrected Calcium Calculator Calculate albumin-corrected calcium. Serum Osmolality Calculator Calculate estimated serum osmolality. Osmolar Gap Calculator Calculate the serum osmolar gap. Winter's Formula Calculator Estimate expected respiratory compensation.

Calculate Anion Gap Online

Enter your electrolyte values above to calculate the anion gap instantly.

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Disclaimer: This calculator is intended for educational and laboratory reference purposes only. It should not replace professional medical advice, laboratory reference intervals, or clinical judgment.