A patient with type 1 diabetes develops diabetic ketoacidosis. Which acid-base disturbance is expected?

• A. Anion gap metabolic acidosis with respiratory compensation
• B. Non-anion gap metabolic acidosis
• C. Metabolic alkalosis
• D. Respiratory alkalosis

Answer: (A)

In diabetic ketoacidosis, lack of insulin drives fat breakdown and ketone production. The accumulating ketone bodies are acids that lower bicarbonate, increasing the anion gap and producing an anion gap metabolic acidosis. The body responds by driving ventilation harder to blow off CO2, giving respiratory compensation (low PaCO2) to help normalize pH. This combination—anion gap metabolic acidosis with appropriate respiratory compensation—fits DKA. The other patterns don’t match: a non‑anion gap acidosis would have a normal anion gap, metabolic alkalosis would raise bicarbonate and pH, and respiratory alkalosis would be a primary increase in pH with low CO2, not a metabolic acidosis.