To determine whether baseline characteristics had an impact on clinical outcomes in the LixiLan‐O trial (N = 1170), we compared the efficacy and safety of iGlarLixi, a titratable fixed‐ratio combination of insulin glargine 100 U (iGlar) and lixisenatide (Lixi) with iGlar or Lixi alone in patients with uncontrolled type 2 diabetes mellitus (T2DM) on oral therapy. Subgroups according to baseline glycated haemoglobin (HbA1c; <8% or ≥8% <64 or ≥64 mmol/mol), T2DM disease duration (<7 or ≥7 years) and body mass index (BMI; <30 or ≥30 kg/m2) were investigated. In all subpopulations, iGlarLixi was consistently statistically superior to iGlar and Lixi alone in reducing HbA1c from baseline to week 30; higher proportions of patients achieved HbA1c <7% (<53 mmol/mol) with iGlarLixi vs iGlar and Lixi alone. Compared with iGlar, iGlarLixi resulted in a substantial decrease in 2‐hour postprandial plasma glucose levels, and mitigation of weight gain, with no differences among subpopulations in incidence of symptomatic hypoglycaemia. iGlarLixi consistently improved glycaemic control compared with iGlar and Lixi alone, without weight gain or increase in hypoglycaemic risk compared with iGlar in the subpopulations tested, regardless of baseline HbA1c, disease duration and BMI.