Iatrogenic hypoglycemia is the most frequent acute complication of insulin therapy in people with type 1 diabetes (T1DM). Recurrent hypoglycemic events initiate a process of habituation, characterized by suppression of hypoglycemic symptoms and lead to hypoglycemia unawareness, which in itself defines a particularly high risk of severe hypoglycemia. Recent evidence suggest a pivotal role for increased brain lactate transport capacity in the pathogenesis of hypoglycemia unawareness. However, there is uncertainty about the magnitude of this effect and whether such excess brain lactate is oxidizes as a glucose-sparing alternative energy source or acts as a metabolic regulator controlling brain glucose metabolism, oxygen consumption and cerebral blood flow.