This study examined the impact of insulin glargine introduction in basal-bolus therapy in type 1 and type 2 diabetic patients with inadequate metabolic control (A1c > 6.9%) using previous NPH insulin regime. In this uncontrolled, retrospective study, 49 patients (28F/21M), average age 24.7 +/- 16.5, mean duration of DM 13.2 +/- 10.1 yrs., 93.1% DM1 patients, received insulin glargine plus mealtime rapid-acting insulin (lispro or aspart) followed by 90-day treatment. We analyzed mean total insulin dose, incidence of hypoglycemic events, convulsive crisis, hyperglycemic complications and A1c levels before and after three months of introduction of glargine therapy. A1c values were determined using the HPLC instrument, with a normal range of 4.3% to 6.9%. After switching to insulin glargine therapy, mean A1c dropped from 10.2 +/- 2.0 to 9.1 +/- 1.8%, with significant impact (p= 0.019). We observed a significant reduction of 0.11 U/kg/day in total insulin dose, dropped from 0.75 U/kg of NPH to 0.64 U/kg of glargine, with significant correlation (p< 0.05). The introduction of glargine therapy was coincident with a decrease of hypoglycemic crisis (p= 0.02), convulsive events due to hypoglycemia (severe hypoglycemic crisis) (p= 0.023) and ketosis (p= 0.001) switching MDI-treated patients with improvement of metabolic control (reduction of A1c levels). This therapy improved quality of life in these patients due to a significant reduction of hypoglycemic (including severe) events, ketosis episodes and total daily insulin dose, with important impact on health public services.