Phase 4 Study to Evaluate Treatment Optimization With Once-daily Insulin Glargine 300 U/mL

Primary Objective: To evaluate the efficacy of switching treatment from twice-daily basal insulin to once-daily insulin glargine (U300) as part of basal bolus regime in terms of glycated hemoglobin improvement (reduction by at least 0.3%), in uncontrolled type 1 diabetes mellitus patients. Secondary Objectives: * To evaluate other efficacy parameters in terms of glycemic control as well as safety including hypoglycemia events, weight changes, and adverse events. * To evaluate the effect of insulin glargine (U300) on diabetes treatment satisfaction and fear of hypoglycemia as well as patient's satisfaction regarding the number of daily injections.