The results of this retrospective observational study show that patients with type 1 or type 2 diabetes, who switch from a predominantly basal-bolus NPH-based regimen to a glargine-based basal-bolus regimen derive significant improvement in glycaemic control (adjusted mean decrease in HbA1c by 0.38% and 0.31%, respectively) within 12 months, without any significant increase in weight, use of prandial boluses, total insulin dose or OAD intensity. This evidence concerns the gene INS and type 2 diabetes mellitus.