Introduction: To assess the changes in glycemic control after initiating or switching to a basal insulin analogue in patients with diabetes mellitus. Methods: A retrospective, observational analysis was conducted using electronic data from a Hong Kong regional hospital. Data from adult patients with type 1 and 2 diabetes mellitus (T1DM and T2DM, respectively) who had been prescribed with basal insulin glargine in 2008-2010, with recorded HbA1c levels at the time of initiation, at 6 and 12 months thereafter, were analysed. Results: Data from 106 eligible patients were analysed. Substantial reduction in HbA1c and fasting sugar levels were reported in both T1DM (Δ HbA1c = 1.5%, Δ FBG = 1.3 mmol/L p < 0.05) and T2DM (Δ HbA1c = 1.2%, Δ FBG = 2.9 mmol/L p < 0.05) patients after 12 months of therapy. A total of 42% of T1DM and 26% of T2DM patients achieved HbA1c levels < 7.0%. After adjustment, T2DM patients who were insulin naive achieved a statistically greater HbA1c reduction (Δ = 1.7%) than those who previous treated with premixed or basal bolus insulin (Δ = 0.3%) (p < 0.05). Percentage of patients experiencing hypoglycaemia reduced from 69% to 62% in T1DM but increased from 26% to 36% in T2DM patients. All hypoglycaemic episodes recorded were either asymptomatic or mild and self-limiting. Only 4% of the patients discontinued treatment at the end of 12 months. Conclusions: In real life clinical practice, a single daily basal insulin analogue therapy provided effective glycemic control with an acceptable risk of mild hypoglycaemia.