What is the normal anion gap range?

The traditional normal range is 8–12 mEq/L. With modern analyzers and albumin-corrected methods, 3–11 mEq/L is often cited. Values above 12 mEq/L are generally considered elevated.

What causes a high anion gap?

Common causes include diabetic ketoacidosis (DKA), lactic acidosis, uremia, salicylate toxicity, methanol or ethylene glycol ingestion, and starvation ketosis — remembered with the mnemonic MUDPILES or GOLDMARK.

Why does albumin affect the anion gap?

Albumin is a negatively charged protein that contributes to unmeasured anions. Low albumin (hypoalbuminemia) falsely lowers the measured anion gap. The correction formula adds 2.5 mEq/L for every 1 g/dL that albumin falls below 4 g/dL.

What does a normal anion gap acidosis mean?

A normal or non-anion-gap metabolic acidosis usually indicates bicarbonate loss, either through the GI tract (diarrhea) or kidneys (renal tubular acidosis), rather than acid accumulation.

Is this calculator a substitute for clinical judgment?

No. This tool is for educational and reference purposes only. Clinical decisions should always be made by a qualified healthcare professional considering the full clinical picture.

Anion Gap Calculator

Enter serum sodium, chloride, and bicarbonate to instantly calculate the anion gap and interpret acid-base status.

Serum Electrolyte Values

All values in mEq/L (mmol/L)

Sodium (Na⁺) 135–145 mEq/L

Chloride (Cl⁻) 95–105 mEq/L

Bicarbonate (HCO₃⁻) 22–29 mEq/L

Albumin optional, g/dL — for corrected AG

Results

Enter values and click Calculate

Anion Gap Reference

AG Range	Classification	Common Causes
< 8 mEq/L	Low (rare)	Hypoalbuminemia, hypermagnesemia, lithium toxicity
8 – 12 mEq/L	Normal	Normal acid-base balance; non-AG acidosis if HCO3 is low
12 – 20 mEq/L	Mildly elevated	Early DKA, mild lactic acidosis, early uremia
> 20 mEq/L	High — significant	Severe DKA, lactic acidosis, toxic ingestion (methanol, ethylene glycol), uremia

This tool is for educational and reference purposes only. Always consult a qualified clinician for medical decisions.

Summary

The anion gap (AG) is calculated as Na − (Cl + HCO3) and represents the concentration of unmeasured anions in serum. A normal anion gap is 8–12 mEq/L (or 3–11 mEq/L when albumin-corrected). A high anion gap indicates metabolic acidosis caused by accumulation of organic acids such as lactate or ketones, while a normal anion gap acidosis suggests bicarbonate loss.

How it works

Enter serum sodium (Na+) in mEq/L.
Enter serum chloride (Cl−) in mEq/L.
Enter serum bicarbonate (HCO3−) in mEq/L.
Optionally enter serum albumin for an albumin-corrected anion gap.
The calculator applies AG = Na − (Cl + HCO3) and displays the result with clinical interpretation.

Use cases

Evaluating a patient with metabolic acidosis in the emergency department.
Distinguishing high-anion-gap from normal-anion-gap metabolic acidosis.
Monitoring electrolyte imbalances in critically ill patients.
Medical student study aid for acid-base physiology.
Quick bedside reference for clinicians reviewing lab results.
Tracking anion gap trends over serial blood draws.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu