The diagnosis of diabetes mellitus is certain in which of the following situations?

The occurrence of hyperglycemic ketoacidosis or hyperglycemic hyperosmolar coma is diagnostic of diabetes mellitus. Similarly, persistent fasting hyperglycemia , even if it is asymptomatic, has been recommended by the National Diabetes Data Group as a criterion for the diagnosis of diabetes. However, abnormal glucose tolerance-whether after eating or after a standard "glucose tolerance test" -can be caused by many factors (e.g., anxiety, infection or other illness, lack of exercise, or inadequate diet). Similarly, glycosuria may have renal as well as endocrinologic causes. Therefore, these two conditions cannot be considered diagnostic of diabetes. Gestational diabetes is diagnosed in women between the twenty-fourth and twenty-eighth weeks of gestation, first using a 50-g oral glucose load if the I-h glucose level >7.8 mmol/L (140 mg/dL); a 100-g oral glucose test is performed after an overnight fast. Gestational diabetes is initially treated with dietary measures; if the postprandial glucose level remains elevated, insulin therapy is often started. About 30% of women with gestational diabetes will eventually develop true dia­betes mellitus.