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Calculates the anion gap delta ratio to evaluate the acid-base response in a high anion gap metabolic acidosis: ΔAG/ΔHCO3 = (measured anion gap − 12) / (24 − measured HCO3). It helps identify mixed acid-base disorders such as a concurrent non-anion gap acidosis or metabolic alkalosis.
ΔAG/ΔHCO3 = ( Anion gap − 12 ) ÷ ( 24 − HCO3 )
1.0–2.0
The delta ratio compares the observed increase in the anion gap to the observed decrease in bicarbonate. A ratio below 1 or above 2 suggests an additional acid-base disorder requiring separate evaluation.
Specialty
Internal MedicineCategory
Internal MedicineDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-16
Formula
Keywords
Normal Range
1.0–2.0
| Classification | Range |
|---|---|
Low mixed high anion gap + non-anion gap acidosis | < 1.0 |
Normal pure high anion gap metabolic acidosis | 1.0–2.0 |
High concurrent metabolic alkalosis or pre-existing high HCO3 | > 2.0 |
Calculates the anion gap delta ratio (ΔAG/ΔHCO3) to evaluate mixed acid-base disorders in high anion gap metabolic acidosis: ΔAG/ΔHCO3 = (AG − 12) / (24 − HCO3).
Ratio < 1.0 suggests a concurrent non-anion gap (hyperchloremic) acidosis. Ratio 1.0–2.0 is consistent with a pure high anion gap acidosis. Ratio > 2.0 suggests a concurrent metabolic alkalosis or pre-existing high bicarbonate.
The delta ratio reconciles the rise in the anion gap with the fall in bicarbonate, revealing hidden mixed acid-base disorders that a simple gap value would miss.
A patient with diarrhea and a high anion gap acidosis has anion gap 23 mEq/L and bicarbonate 12 mEq/L.
Inputs:
ΔAG/ΔHCO3 = (23 − 12) / (24 − 12) = 11/12 ≈ 0.92 — below 1, suggesting a mixed high anion gap plus non-anion gap acidosis.
The bicarbonate fall exceeds the anion gap rise, indicating a concurrent non-anion gap (hyperchloremic) acidosis such as diarrhea or a renal tubular acidosis.
The bicarbonate is higher than expected for the gap elevation, suggesting a concurrent metabolic alkalosis or pre-existing high bicarbonate.
Confirming a high anion gap acidosis
Normal anion gap acidosis
Evaluating the PaCO2 response
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. Mixed acid-base interpretation requires integration of the full chemistry panel, ABG, and clinical context.