What is metformin’s primary action in type 2 diabetes and a key safety concern?

• A. Decreases hepatic glucose production and improves insulin sensitivity; risk of lactic acidosis in renal impairment or dehydration.
• B. Increases pancreatic insulin secretion; risk of hypoglycemia.
• C. Inhibits glucose absorption in the gut; risk of GI upset.
• D. Stimulates glycogenolysis; risk of hyperglycemia.

Answer: (A)

Metformin primarily lowers glucose by reducing hepatic glucose production and improving insulin sensitivity, especially in muscle. It does this mainly by inhibiting hepatic gluconeogenesis and activating AMPK, which decreases liver glucose output and enhances peripheral glucose uptake. A key safety concern is lactic acidosis, particularly in patients with renal impairment or dehydration, because metformin is cleared by the kidneys and can accumulate under those conditions. It’s not about increasing insulin secretion from the pancreas, inhibiting intestinal glucose absorption, or stimulating glycogen breakdown, which are mechanisms seen with other classes of diabetes meds.