Unawareness of hypoglycaemia (reduced ability/failure to recognize hypoglycaemia symptoms at the physiological threshold of 3.0 mmol/l) occurs frequently in type 1 diabetes mellitus, and patients are then at risk for severe hypoglycaemia. Unawareness of hypoglycaemia is the result of earlier frequent episodes of hypoglycaemia (iatrogenic). Likewise, a history of hypoglycaemia induces unawareness, while meticulous prevention of hypoglycaemia can reverse hypoglycaemia unawareness. Therefore, it is essential that insulin therapy regimens for type 1 diabetes mellitus be designed not only to maintain near-normoglycaemia, but also to minimize hypoglycaemia. Such a goal is feasible as long as (1) a rational plan of insulin therapy is adopted, including appropriate use of the short-acting insulin analogue lispro, (2) blood glucose is properly monitored, (3) blood glucose targets are individualized, and (4) education programs are widely implemented.