The most appropriate treatment for this patient's diabetes mellitus while hospitalized is a weight-based treatment plan that includes basal and prandial insulin. Hyperglycemia in the hospital is associated with poor outcomes. According to the American Diabetes Association and American Association of Clinical Endocrinologists, glucose goals in hospitalized patients in a non-ICU setting are premeal values less than 140 mg/dL (7.8 mmol/L) and random values less than 180 mg/dL (10 mmol/L). The American College of Physicians recommends avoiding values less than 140 mg/dL (7.8 mmol/L) to decrease the risk of hypoglycemic complications. The patient's plasma glucose values exceed the recommended guidelines and require treatment.

Oral agents do not have safety or efficacy data for use in the hospital. Glipizide is an insulin secretagogue that can potentially induce hypoglycemia in the hospital setting, particularly with unpredictable changes in oral intake.

With metformin use, hospitalized patients can develop poor organ perfusion, which can increase the risk of lactic acidosis. Intravenous contrast dye can also impair kidney function in the setting of metformin use in the hospital. Reinitiation of the patient's home regimen of metformin at or near the time of discharge is most appropriate after all procedures have been completed and organ function is stable and glucose levels have returned to baseline values.

Sliding-scale insulin is nonphysiologic and can result in large fluctuations in blood glucose levels. Sliding-scale insulin is not recommended as the sole insulin therapy in the hospital setting.