A nurse is caring for a client who was prescribed metformin 6 months ago. Which of the following findings indicates a positive response to the medication?

Metformin is a biguanide antidiabetic medication that lowers blood glucose by decreasing hepatic glucose production and improving insulin sensitivity. A decreased HbA1c (glycated hemoglobin) reflects improved long-term blood glucose control over the past 2–3 months — the primary indicator of metformin effectiveness. Metformin does not affect iron levels, urinary continence, or HDL cholesterol significantly.