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Type 1 diabetes new diagnosis — USMLE Step 3 MCQ

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ModeratePediatrics (well-child, chronic management)Type 1 diabetes new diagnosisUSMLE Step 3

A 12-year-old girl has polyuria, polydipsia, weight loss, and fatigue. Glucose is 356 mg/dL, bicarbonate is 23 mEq/L, and urine ketones are trace. BMI is 18 kg/m2. Which of the following is the most likely diagnosis?

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Correct answer: D — Type 1 diabetes mellitus

Classic hyperglycemic symptoms with weight loss in a lean child suggest type 1 diabetes, even without ketoacidosis.

Reference: American Diabetes Association Standards of Care in Diabetes—2026