Abstract Background Although the number of antihyperglycemic agents has expanded significantly, sulfonylureas (in particular gliclazide) remain an important option because of a variety of patient and health system factors. The large, real world, observational, and international EASYDia trial evaluated the effectiveness of gliclazide modified release (MR) 60 mg in individuals with type 2 diabetes with a broad range of diabetes history, body mass index (BMI) and background antihyperglycemic treatment. Methods A total of 7170 participants from eight countries, age ≥ 35 years with HbA1c ≥ 7.5% and not treated with insulin, were prescribed 30–120 mg of gliclazide MR 60 mg once daily. HbA1c goals were individualized and dosing uptitrated, as required, over the 6-month long study. In this post hoc subanalysis, efficacy endpoints were analyzed according to stratified baseline HbA1c levels, weight and glucose-lowering regimens. Episodes of hypoglycemia requiring assistance were documented. Results At baseline, mean age was 58.9 years, HbA1c 8.8%, BMI 30.1 kg/m2, and diabetes duration 5.1 years. At study end, clinically significant HbA1c improvements (mean change − 1.78%) were noted across all baseline HbA1c strata (> 7.0 to ≤ 8.0%, > 8.0 to ≤ 9.0%, > 9.0 to ≤ 10.0%, and > 10.0%), BMI classifications (18.5 to < 25.0, 25.0 to < 30.0, and ≥ 30.0 kg/m2), and regardless of the original diabetes treatment regimen (P < 0.001 in all cases). In contrast to the subgroups with BMI 25.0–30.0 and ≥ 30.0 kg/m2 that registered weight losses of 0.9 and 2.2 kg, respectively (P < 0.001 vs. baseline weight); the BMI 18.5–24.9 kg/m2 subgroup gained a mean 0.5 kg (P < 0.02 vs. baseline weight). Severe hypoglycemic events were rare (0.06%). Conclusions Progressive gliclazide MR 60 mg uptitration was well tolerated and lowered HbA1c across a broad range of HbA1c, BMI and background glucose-lowering therapy. Weight loss was noted when BMI was ≥ 25.0 kg/m2. Individuals with the highest baseline HbA1c and BMI experienced the greatest HbA1c and weight improvements. Trial registration ISRCTN Registry ISRCTN00943368 on 1st July 2011