Changes in carbohydrate metabolism, admittedly one of the most prevalent etiologies of Méière's syndrome, can be diagnosed early by 5-hour glucose and insulin curves with a 100-g glucose load, a test more sensitive than those traditionally used in investigating impaired glucose tolerance or diabetes mellitus. This study investigated carbohydrate metabolism characteristics in 64 patients with typical Ménière's disease. We demonstrated that 72% of them had some variable degree of hyperinsulinemia as shown by their plasma insulin curves, whereas alterations on the glucose curve (reactive hypoglycemia or hyperglycemia) were found for only 21%. More advanced hyperinsulinemic conditions (i.e., glucose intolerance or diabetes mellitus) were usually associated with changes in lipid profiles and with a central pattern of fat distribution and systemic hypertension. We found a very strong correlation between insulin concentrations measured by chemoluminescence and by radioimmunoassay; the latter, however, showed values 1.3 times higher than those measured by chemoluminescence. These findings confirm the need to include 5-hour glucose and insulin curves in the diagnostic routine when investigating Ménière's disease. In that way, an early diagnosis of hyperinsulinemia, the metabolic change most often involved in the pathogenesis of cochleovestibular disorders, can be made.