1Albumin-Corrected Anion Gap — Guide
Corrected AG = Measured AG + 2.5 × (4.0 − Albumin g/dL)
Delta-Delta = (Corrected AG − 12) ÷ (24 − HCO₃)
Normal Delta-Delta Reference: 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)
2Frequently Asked Questions
3Related Calculators
4Expanded Deep-Dive Guide
Understanding Hypoalbuminaemia Muffling
Because serum albumin serves as the main unmeasured biological buffer anion in circulating plasma systems, shifts in its concentration structurally hide or warp underlying toxic trends. Failing to correct for severe hypoalbuminaemia frequently causes hidden High Anion Gap Metabolic Acidosis (HAGMA) states to be misdiagnosed as uncomplicated or minor metabolic disruptions.
Applying the Reference Adjustments
When computing advanced critical values within multi-system triage zones, always ensure you swap out the traditional uncorrected anion variables with advanced corrected equivalents before generating your final target Delta-Delta metric streams. This safeguards treatment protocols from accidental under-resuscitation errors.
In critical care medicine, severe hypoalbuminaemia hides dynamic metabolic acidosis trends by falsely down-toggling structural anion metrics. Always substitute corrected values inside diagnostic math profiles to protect diagnostic specificity.
Medical disclaimer: This calculator is for educational and clinical decision-support purposes only. It does not replace clinical judgment or specialist consultation. RxMedCalc is not liable for clinical decisions made solely on this tool.