The nurse practitioner suspects type 1 diabetes mellitus because a 3-year-old female presents with:

Rationale: A. Increased weight gain is not typical of type 1 diabetes; lethargy and nocturia alone are nonspecific. B. A persistent vaginal yeast infection, weight loss, and urinary frequency are classic signs of type 1 diabetes mellitus in young children. Hyperglycemia provides a favorable environment for yeast infections, causes osmotic diuresis (frequent urination), and leads to unintentional weight loss despite normal or increased appetite. C. Increased activity and frequent stools are not typical presenting features of type 1 diabetes. D. Weight gain is not consistent with type 1 diabetes; increased thirst and nocturia may occur, but the weight loss seen in option B is more indicative.