Acid–base
Anion gap calculator — with albumin correction and delta ratio
Calculate the serum anion gap, correct it for hypoalbuminaemia, and derive the delta ratio to detect a concurrent second acid–base disorder. For use by licensed clinicians.
Albumin-corrected anion gap
12.0mEq/L
Uncorrected gap 12.0 mEq/L. Potassium is not included in this formula.
For use by licensed clinicians as a calculation aid only. It does not account for the individual patient context, and it does not replace clinical judgement or your local protocol. Verify any value before it informs a dose or a decision.
Equation used
Anion gap = Na⁺ − (Cl⁻ + HCO₃⁻). Corrected AG = AG + 2.5 × (4.0 − albumin g/dL). Delta ratio = (corrected AG − 12) / (24 − HCO₃⁻).
Source
Figge J et al., Critical Care Medicine, 1998
Albumin is the dominant unmeasured anion, so an uncorrected gap in a hypoalbuminaemic patient routinely reads as normal while a genuine high-anion-gap acidosis is present.
Common questions
Should potassium be included in the anion gap?
The formula here excludes potassium, which is the more common convention and the one the 12 mEq/L reference range corresponds to. Including potassium raises the gap by roughly 4 and requires a correspondingly higher reference range.
What does the delta ratio tell me?
It compares the rise in anion gap with the fall in bicarbonate. Below 0.4 suggests a concurrent normal-anion-gap acidosis; above 2 suggests a concurrent metabolic alkalosis or a pre-existing raised bicarbonate from chronic respiratory acidosis.