A teenage girl presents with polyuria, polydipsia, dehydration, and a high plasma glucose with metabolic acidosis. The most likely diagnosis is which of the following?

• A. Hyperosmolar nonketotic hyperglycemia
• B. Diabetic ketoacidosis
• C. Chronic corticosteroid use
• D. Gestational diabetes

Answer: (B)

This presentation is classic for diabetic ketoacidosis. When insulin is deficient, the body cannot use glucose effectively and turns to fat breakdown, producing ketone bodies. Those ketones accumulate, causing an anion-gap metabolic acidosis, while high glucose drives osmotic diuresis that leads to dehydration. The combination of polyuria, polydipsia, dehydration, and high glucose with acidosis is typical of DKA, especially in teenagers with new-onset type 1 diabetes.

Hyperosmolar nonketotic hyperglycemia would involve very high glucose with dehydration but little or no ketosis or acidosis, and it usually occurs in older individuals with type 2 diabetes. Chronic corticosteroid use can raise blood glucose but does not produce the ketosis-driven acidosis seen in DKA. Gestational diabetes is pregnancy-related and not a consideration in a nonpregnant teenager.