Albumin-Corrected Anion Gap
mmol/L
mmol/L
mmol/L
g/dL (normal ~4.0 g/dL)
Measured AG
—
mmol/L
Corrected AG
—
mmol/L
Delta-Delta
—
ratio
Albumin-Corrected Anion Gap — Guide
Anion Gap = Na − (Cl + HCO₃) [normal 8–12 mmol/L]
Corrected AG = Measured AG + 2.5 × (4.0 − Albumin g/dL)
Delta-Delta = (AG − 12) ÷ (24 − HCO₃)
Normal Delta-Delta: 1–2
Corrected AG = Measured AG + 2.5 × (4.0 − Albumin g/dL)
Delta-Delta = (AG − 12) ÷ (24 − HCO₃)
Normal Delta-Delta: 1–2
Why Correct for Albumin?
Albumin is a negatively charged protein that contributes approximately 2.5 mmol/L to the anion gap per 1 g/dL of albumin. In hypoalbuminaemia (common in ICU, liver disease, nephrotic syndrome, malnutrition), the anion gap is falsely lowered — a high-AG metabolic acidosis may appear as a normal-AG acidosis. For every 1 g/dL drop in albumin below 4.0, the measured AG underestimates true AG by ~2.5 mmol/L.
Delta-Delta Ratio Interpretation
- <0.4: Normal AG metabolic acidosis only (hyperchloraemic) — no high AG component
- 0.4–1.0: Combined high AG + normal AG metabolic acidosis — two simultaneous acidoses
- 1–2: Pure high anion gap metabolic acidosis — uncomplicated
- >2: High AG acidosis + concurrent metabolic alkalosis — the bicarbonate is higher than expected for the degree of AG elevation
High AG Causes — MUDPILES
- Methanol poisoning
- Uraemia (chronic kidney disease)
- Diabetic ketoacidosis (DKA)
- Propylene glycol (IV lorazepam, some medications)
- Isoniazid / Iron toxicity
- Lactic acidosis (Type A: hypoperfusion; Type B: metformin, liver disease, malignancy)
- Ethylene glycol poisoning
- Salicylate (aspirin) toxicity
Normal AG Causes (Hyperchloraemic)
- Diarrhoea — GI bicarbonate loss
- Renal tubular acidosis (RTA) Types 1, 2, 4
- Normal saline administration (dilutional/hyperchloraemic acidosis)
- Addison's disease / hypoaldosteronism
- Carbonic anhydrase inhibitors (acetazolamide)
Related Calculators
⚠ Medical Disclaimer: Acid-base interpretation requires ABG correlation, clinical context, and electrolyte confirmation. The anion gap formula varies by laboratory (some include K⁺). Delta-delta ratio is a guide — use alongside clinical assessment and ABG. Albumin correction is especially important in ICU, liver disease, and malnutrition.