Which hydrogen ion–producing state is most likely to cause an anion gap metabolic acidosis?

• A. Hyperchloremic metabolic acidosis
• B. Respiratory acidosis
• C. Metabolic alkalosis
• D. Diabetic ketoacidosis

Answer: (D)

An elevated anion gap metabolic acidosis happens when acids that contain unmeasured anions accumulate in the blood. In diabetic ketoacidosis, insulin deficiency drives lipolysis and hepatic ketogenesis, yielding ketone bodies—beta-hydroxybutyrate and acetoacetate—that are strong acids and carry negative charges not routinely measured on a standard anion gap panel. Their accumulation lowers bicarbonate, and the body’s chloride tends to rise to maintain electroneutrality, increasing the measured anion gap Na − (Cl + HCO3). This pattern is the classic presentation of high anion gap metabolic acidosis.

Hyperchloremic metabolic acidosis, by contrast, involves loss of bicarbonate with a compensatory increase in chloride, so the anion gap remains normal. Respiratory acidosis is a CO2-retention problem and does not produce an unmeasured anion–driven gap in the same way, and metabolic alkalosis is the opposite process, not an acidosis.