In nephrology, the delta ratio, or "delta-delta" (denoted Δ/Δ), is a formula that can be used to evaluate whether a mixed acid–base disorder (metabolic acidosis) is present, and if so, assess its severity. The anion gap (AG) without potassium is calculated first and if a metabolic acidosis is present, results in either a high anion gap metabolic acidosis (HAGMA) or a normal anion gap acidosis (NAGMA). A low anion gap is usually an oddity of measurement, rather than a clinical concern.