What acid-base disturbance is characteristic of diabetic ketoacidosis?

• A. Metabolic alkalosis
• B. Normal anion gap metabolic acidosis
• C. Non-anion gap metabolic acidosis
• D. High anion gap metabolic acidosis

Answer: (D)

In diabetic ketoacidosis, lack of insulin drives excess production of ketone bodies (acetoacetate and beta-hydroxybutyrate). These ketone bodies are unmeasured anions that accumulate in the blood, consuming bicarbonate as they are buffered. The result is a metabolic acidosis with a raised anion gap. The body tries to compensate by hyperventilating (Kussmaul respiration) to blow off CO2 and raise pH.

So the characteristic pattern is a high anion gap metabolic acidosis due to ketoacids. This differentiates it from metabolic alkalosis (pH high, bicarbonate high), or from normal or non–anion gap acidoses (where the anion gap remains normal and the acidosis stems from bicarbonate loss or other non-ketone mechanisms). A numerical clue is an increased anion gap calculated as Na − (Cl + HCO3), often well above the normal ~12 mEq/L in DKA.