Delta Ratio Acid-Base Calculator

About this calculator

The delta ratio (also called delta-delta) helps clinicians spot a hidden second acid-base disorder underneath an obvious high anion-gap metabolic acidosis (HAGMA), by comparing how much the anion gap has risen against how much the bicarbonate has fallen: delta ratio = (measured anion gap − normal anion gap) divided by (normal bicarbonate − measured bicarbonate).

In a “pure” HAGMA, each mole of unmeasured acid that widens the gap should consume roughly one mole of bicarbonate, putting the ratio near 1–2. A ratio below 1 suggests a concurrent normal-anion-gap (hyperchloremic) metabolic acidosis is dropping the bicarbonate more than the gap alone explains — common in diarrhea or renal tubular acidosis on top of, say, diabetic ketoacidosis. A ratio above 2 suggests the bicarbonate is not falling as much as expected, pointing to a coexisting metabolic alkalosis or a chronic compensated respiratory acidosis.

This calculator takes the anion gap and bicarbonate values from a basic metabolic panel and returns the delta ratio along with what it suggests about a mixed disorder.