What is the normal anion gap?

The traditional normal range is 8–12 mEq/L with modern analyzers. Older references cite 12 ± 4 mEq/L. Values above 12 are generally considered elevated and warrant further workup.

What causes a high anion gap?

Common causes are recalled with MUDPILES: Methanol, Uremia, Diabetic ketoacidosis, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates. The newer GOLDMARK mnemonic adds Glycols, Oxoproline, L-lactate, D-lactate, Methanol, Aspirin, Renal failure, Ketoacidosis.

Why correct for albumin?

Albumin is a major unmeasured anion. Each 1 g/dL fall below 4 g/dL lowers the measured AG by roughly 2.5 mEq/L. Hypoalbuminemia can mask a true high-AG acidosis, so the corrected AG is more reliable in patients with liver disease, malnutrition, or critical illness.

How do I interpret the delta gap?

Delta gap = (AG − 12) / (24 − HCO3). A ratio 2 suggests a superimposed metabolic alkalosis.

Is this tool a substitute for clinical judgment?

No. This calculator is for educational and reference use only. Acid-base interpretation requires correlation with arterial blood gas, clinical history, and physical examination by a qualified clinician.

Anion Gap Calculator

Name: Anion Gap Calculator
Availability: InStock
Author: Nham Vu

Enter Na, Cl, HCO3 (and optionally albumin) to get the anion gap, albumin-corrected AG, and delta gap for mixed acid-base disorder detection.

Serum Values

Required values in mEq/L (mmol/L)

Sodium (Na⁺) normal 135–145

Chloride (Cl⁻) normal 95–105

Bicarbonate (HCO₃⁻) normal 22–29

Albumin optional, g/dL — enables corrected AG

Results

Enter values and click Calculate

Quick Reference

Anion Gap Ranges

AG (mEq/L)	Classification
< 8	Low — hypoalbuminemia, hypermagnesemia
8 – 12	Normal
12 – 20	Mildly elevated — early DKA, lactic acidosis
> 20	High — severe HAGMA (DKA, toxic ingestion)

Delta Gap Ratio

Ratio	Interpretation
< 0.4	Pure normal-AG acidosis
0.4 – 1.0	Mixed high-AG + normal-AG acidosis
1.0 – 2.0	Pure high-AG metabolic acidosis
> 2.0	High-AG acidosis + metabolic alkalosis

For educational and reference use only. All clinical decisions require evaluation by a qualified healthcare professional.

Summary

Enter Na, Cl, HCO3 (and optionally albumin) to get the anion gap, albumin-corrected AG, and delta gap for mixed acid-base disorder detection.

How it works

Enter serum sodium (Na+), chloride (Cl−), and bicarbonate (HCO3−) in mEq/L.
Optionally enter serum albumin (g/dL) to get the albumin-corrected anion gap.
The calculator applies AG = Na − (Cl + HCO3) and classifies the result.
If albumin is provided, corrected AG = AG + 2.5 × (4 − albumin).
Delta gap = (AG − 12) / (24 − HCO3) detects mixed acid-base disorders.
Interpretation panels explain the clinical meaning of each result.

Use cases

Emergency workup of a patient with metabolic acidosis.
Distinguishing high-AG from normal-AG (hyperchloremic) metabolic acidosis.
Unmasking a coexisting metabolic alkalosis or normal-AG acidosis with the delta gap.
Adjusting for hypoalbuminemia in critically ill or cirrhotic patients.
Medical education and acid-base physiology study.
Serial monitoring of electrolyte trends in the ICU.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu