Data from the systematic review indicated sulfonylureas alone and in combination were associated with hypoglycemia. Lipid levels varied widely across medication types, with metformin demonstrating favorable effects for all lipid classes. Thiazolidinediones were also associated with double the risk of congestive heart failure compared with sulfonylureas.2 In fact, the FDA placed boxed warnings on the thiazolidinediones, rosiglitazone and pioglitazone, displaying the contraindication for patients with serious or severe heart failure.3 Other results showed metformin was commonly associated with gastrointestinal side effects. In addition, patients taking thiazolidinediones had a 1.5-fold increased risk for fractures compared with metformin alone or in combination with sulfonylureas. There was a lower risk for lactic acidosis associated with metformin compared with metformin and sulfonylureas.