Diabetes mellitus is rapidly increasing, diabetic patients are likely to undergo surgical procedures more than non-diabetic patients, the hospital stay of diabetic patients is longer, and diabetic patients have increased mortality and morbidity. The correct treatment of diabetic patients in the perioperative period is crucial to improve clinical outcomes. Diabetic patients must be carefully evaluated for cardiovascular risk, keeping in mind micro- and macroangiopathic diabetic complications. Metabolic control deserves great attention because hyperglycemia is related to increased complications and worse outcomes. Insulin infusion regimens to achieve near normoglycemia must be implemented in surgical and critically ill patients.