In untreated diabetes mellitus, which metabolic change most directly contributes to metabolic acidosis?

• A. Increased lactic acid
• B. Increased ketone production
• C. Decreased glucose production
• D. Increased bicarbonate

Answer: (B)

Uncontrolled insulin deficiency drives rapid lipolysis, delivering fatty acids to the liver where they are converted into ketone bodies. These ketone bodies are acidic, so their accumulation directly lowers blood pH and causes the metabolic acidosis seen in diabetic ketoacidosis. Lactic acid can cause acidosis in other scenarios, but it isn’t the primary driver here. In untreated diabetes, hepatic glucose production is actually elevated due to increased gluconeogenesis and glycogenolysis, not reduced, so changes in glucose production don’t directly cause this acidosis. Bicarbonate buffers acid; as ketones accumulate, bicarbonate is consumed and falls, not increases.