Anion Gap Calculator

The Anion Gap Calculator helps healthcare professionals assess acid-base disorders by calculating the difference between measured cations (positively charged ions) and anions (negatively charged ions) in blood serum.

What is the Anion Gap?

The anion gap is a calculated value that represents the difference between unmeasured anions and unmeasured cations in the blood. It’s an important tool for:

Evaluating acid-base disorders
Diagnosing various types of metabolic acidosis
Monitoring critical illness
Assessing electrolyte imbalances

Clinical Significance

The anion gap helps differentiate between different types of metabolic acidosis:

High Anion Gap Metabolic Acidosis

Common causes include:

Diabetic ketoacidosis
Lactic acidosis
Toxic ingestions
Renal failure

Normal Anion Gap Metabolic Acidosis

Common causes include:

Diarrhea
Renal tubular acidosis
Early renal failure
Carbonic anhydrase inhibitors

Calculation Methods

Standard Anion Gap Formula

AG = [Na⁺] - ([Cl⁻] + [HCO₃⁻])

With Potassium

AG = [Na⁺] + [K⁺] - ([Cl⁻] + [HCO₃⁻])

Albumin-Corrected Anion Gap

Corrected AG = AG + 2.5 × (4.0 - [Measured Albumin])

Where:

Na⁺: Sodium
K⁺: Potassium
Cl⁻: Chloride
HCO₃⁻: Bicarbonate

Normal Values

Without Potassium

Normal range: 3-11 mEq/L
High: >11 mEq/L
Low: <3 mEq/L

With Potassium

Normal range: 5-16 mEq/L
High: >16 mEq/L
Low: <5 mEq/L

Interpreting Results

High Anion Gap

May indicate:

Ketoacidosis
Lactic acidosis
Toxic ingestions
Renal failure
Severe diarrhea

Normal Anion Gap

May indicate:

Normal acid-base status
Non-anion gap metabolic acidosis
Compensated metabolic disorders

Low Anion Gap

May indicate:

Hypoalbuminemia
Multiple myeloma
Dilutional states
Laboratory error

Important Notes

All values should be in mEq/L (or mmol/L, which are equivalent for these ions)
Results should be interpreted in clinical context
Consider correcting for albumin in critically ill patients
Laboratory error should always be considered
Follow up abnormal results with appropriate clinical evaluation

This calculator is intended for use by healthcare professionals. Always consult with a qualified medical professional for interpretation of results and medical advice.