The measurement of the blood sugar concentration serves as a simple parameter for the diagnosis and differentiation of the various disorders of the blood sugar level up to diabetes mellitus. The disturbed glucose tolerance is evident from a slightly pathological fasting glycaemia. However, the oral glucose tolerance test shows abnormal values. Impaired glucose tolerance is likely to be widespread in the Western population. In particular, patients with a metabolic syndrome from a complex of abdominal obesity, hypertriglyceridemia, arterial hypertension an impaired carbohydrate metabolism are exposed to this risk. Dysfunctional glucose tolerance is quite manifold in terms of negative effects. Well known are e.g. changes in insulin homeostasis and insulin effectiveness or a perturbed acid-base buffer system with acid overload.