Because of several factors, including a change in the hormonal behavior, the postoperative period is at high risk for the diabetic patient to present a metabolic complication. On the other hand, a diabetic metabolic disorder may be secondary and reveal a severe underlying complication (sepsis...). Ketoacidosis is the consequence of an absolute or relative lack of insulin and occurs mainly in insulin dependent diabetic patients. Its incidence should be very low during the postoperative period since insulin protocols are systematically used. The main clinical and biological signs are a polypnea, signs of dehydration, an hyperglycemia associated with a high anion gap metabolic acidosis and the presence of ketoacids in the urine. Its treatment is mainly based on an active rehydration and an insulin and potassium supply. Sodium bicarbonate should not be used systematically any more, even during severe acidosis. Hyperosmolar non ketotic states affects insulin nondependent and older diabetic patients for the most part and occurs under similar conditions than ketoacidosis, revealing most of the time a severe underlying complication. Clinical and biological manifestations include a severe dehydration, alterations in consciousness and a major hyperglycemia associated to a moderate or mild metabolic acidosis. Its main treatment is an active rehydration and insulin plus potassium in a second time. Hypoglycemia is usually the consequence of a mistake in the diabetes care and in the insulin management. Every sickness or consciousness disorder occurring in a diabetic patient treated with insulin should lead to perform a blood glucose measurement. In case of severe manifestations, glucose should be administered in emergency, orally if the patient is conscious or intravenously if he is not. Lactic acidosis occurring during the postoperative period in a diabetic patient is usually non specific of diabetic disease and reflects the existence of an underlying complication (sepsis, hemorrhage, hypoxia,...), as it would in an non diabetic patient. Lactic acidosis due to a treatment with metformin is now very rare and occurs almost only in patients having a contraindication to the use of metformin.