Which of the following is a hallmark laboratory finding in diabetic ketoacidosis?

• A. Glucose > 250 mg/dL
• B. Bicarbonate < 15 mEq/L
• C. pH < 7.3
• D. Ketonemia

Answer: (D)

In diabetic ketoacidosis the defining change is the production of ketone bodies due to a lack of insulin. When insulin is deficient, the body increases lipolysis and sends fatty acids to the liver, where they are converted into ketones (acetoacetate and beta-hydroxybutyrate). These ketones accumulate in the blood, producing ketonemia, which is a direct reflection of the ketogenesis driving the illness. Detecting ketones in the blood (or urine) is the hallmark that confirms this ketogenic metabolic state.

Hyperglycemia (glucose > 250 mg/dL) and metabolic acidosis with low bicarbonate or a low pH are indeed characteristic features of DKA, but they can occur in other conditions as well. The presence of ketones specifically points to the underlying process of insulin deficiency with increased fat breakdown, making ketonemia the most distinctive lab finding in this scenario.