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ICU, Emergency & Nephrology Utility

Anion Gap Clinical Calculator

Evaluates serum anion gap with automated Figge albumin correction and Delta-Delta ratio calculation to identify High Anion Gap Metabolic Acidosis (HAGMA) and mixed acid-base disorders.

Diagnostic Rigor

Critical Care Protocol

Interactive Anion Gap & Delta Ratio Tool

Figge Albumin Correction & Acid-Base Triage

Sodium (Na⁺)

mEq/L

Normal: 135–145

Chloride (Cl⁻)

mEq/L

Normal: 96–106

Bicarbonate (HCO₃⁻)

mEq/L

Normal: 22–28

Serum Albumin

g/dL

Normal: 3.5–5.0 g/dL

Include Potassium (K⁺) in formula: [Na⁺ + K⁺] - [Cl⁻ + HCO₃⁻]

Albumin-Corrected Anion Gap (Figge)

23mEq/L

Observed AG: 20 mEq/L (Correction: +3)

Elevated Gap (HAGMA) — 23 mEq/L

Reference Interval: 4–12 mEq/L

0 (Low Gap)Normal (4–12)30+ (Severe Acidosis)

Clinical Interpretation

High Anion Gap Metabolic Acidosis (HAGMA). Indicates circulating unmeasured organic/inorganic anions. Screen immediately for Ketoacidosis (DKA, AKA), L-Lactate (sepsis, shock), Uremia (renal failure), or Toxic Ingestions (GOLD MARK mnemonic).

Delta-Delta (Δ/Δ) Acid-Base RatioRatio: 1.83

Delta Ratio 1.2–2.0: Classic HAGMA; commonly observed in lactic acidosis due to intracellular buffering shifts.

Etiologies of High Anion Gap Metabolic Acidosis (GOLD MARK Mnemonic)

When serum anion gap is elevated (> 12 mEq/L), unmeasured organic or inorganic acids are circulating. The modern GOLD MARK mnemonic outlines the primary clinical causes:

GGlycols (Ethylene & Propylene Glycol)

Antifreeze ingestion, toxic solvent exposure. Often presents with high osmolar gap and acute renal injury.

OOxoproline (5-Oxoproline / Pyroglutamic Acid)

Associated with chronic acetaminophen (paracetamol) usage in malnourished or female septic patients.

LL-Lactate (Lactic Acidosis)

Tissue hypoperfusion, septic shock, cardiogenic collapse, severe hypoxia, or mesenteric ischemia.

DD-Lactate (Short Bowel Syndrome)

Bacterial carbohydrate fermentation in patients with extensive small bowel resection. Normal L-lactate assay.

MMethanol

Formic acid accumulation resulting in optic disc hyperemia, blindness, and profound metabolic acidosis.

AAspirin (Salicylate Toxicity)

Causes mixed respiratory alkalosis (central hyperventilation) and high anion gap metabolic acidosis.

RRenal Failure (Uremia)

Advanced acute kidney injury or Stage 4-5 CKD with impaired clearance of organic sulfates and phosphates.

KKetoacidosis (DKA, AKA, Starvation)

Acetoacetate and beta-hydroxybutyrate accumulation in diabetic ketoacidosis, chronic alcohol abuse, or prolonged fasting.

Mathematical Specifications & Albumin Correction

Standard Anion Gap: AG = Na⁺ - (Cl⁻ + HCO₃⁻)

Albumin Corrected AG: AG_corr = AG_obs + 2.5 × (4.0 - Albumin g/dL)

Delta Ratio: Δ/Δ = (AG_corr - 12) / (24 - HCO₃⁻)

In critically ill patients, hypoalbuminemia is ubiquitous. Because serum albumin provides approximately 75% of the normal unmeasured anion pool, failing to correct for hypoalbuminemia masks clinically significant high anion gap acidosis. For every 1.0 g/dL drop in serum albumin below 4.0 g/dL, the apparent anion gap drops by ~2.5 mEq/L.

Companion Renal & Metabolic Tools

eGFR Calculator (CKD-EPI 2021)

Race-free equation for KDIGO CKD G1–G5 staging.

Creatinine Clearance (Cockcroft-Gault)

Calculates CrCl with automated IBW and ABW for antibiotic dosing.

Kidney Function Test (KFT) Panel

Reference intervals for Creatinine, BUN, Uric Acid & Electrolytes.

HbA1c to Glucose Converter

Calculate Estimated Average Glucose (eAG) from glycated hemoglobin.

Electrolyte Quality Guard

Serum electrolyte values should be obtained concurrently from a single non-hemolyzed blood specimen. Hemolysis significantly elevates potassium and can distort bicarbonate calculations.

Standard Ion-Selective Electrode (ISE) Baseline