Landgraf W, et al. - In insulin-naive people with type 2 diabetes mellitus (T2DM) starting basal insulin glargine 100 U/mL (Gla-100), researchers explored the connection between baseline fasting C-peptide (FCP) and outcomes. Post-hoc pooled analysis of 9 randomised, treat-to-target trials in people with T2DM that are inadequately controlled by oral anti-hyperglycaemic drugs initiating once-daily Gla-100. According to FCP (≤ 0.40, > 0.40-1.20, > 1.20-2.00, > 2.00 nmol/L), 2,165 participants were stratified at baseline. At 24 weeks, glycaemic control, body weight, insulin dose and hypoglycaemia were determined. At baseline low FCP levels were linked to longer known diabetes duration, lower BMI, and higher FPG. FCP levels identified T2DM individuals with various responses to Gla-100 basal insulin. A low FCP identifies a significantly insulin-deficient, insulin-sensitive subgroup/phenotype with an enhanced risk of hypoglycaemia, requiring low initial basal insulin dose, cautious titration and earlier prandial glucose-lowering therapy supplementation. According to multivariable regression analysis, baseline FCP, concomitant sulfonylurea use, and endpoint HbA1c were strong predictors of hypoglycaemia.