ObjectivesTo explore parameters that may determine the improvement in C-peptide levels in patients with type 2 diabetes (T2D) receiving continuous subcutaneous insulin infusion (CSII) therapy. MethodsThe trial included a lead-in period for collecting baseline parameters and correcting hyperglycemia, a 4-day CGM period, and a 2–3 weeks treatment period. After screening, patients were hospitalized and randomized to the metformin add-on NovoRapid group or the Prandilin group. Once the glycemic target was reached, all patients underwent a 4-day CGM, with treatments maintained for 2–3 weeks. OGTTs were performed at baseline and endpoint. The primary endpoint was identifying factors contributing to better β-cell function recovery after CSII therapy. ResultsA total of 99 recruited patients were admitted as inpatients and achieved glycemic control within 3.8 ± 1.1 days. Of these, 83 (84 %) patients showed improvement in C-peptide levels, while 16 (16 %) did not show any change in C-peptide levels at the endpoint. Pearson analysis showed a negative correlation between the incremental AUC of glucose concentration (from 0700 to 1000) and the increase in incremental AUC of C-peptide levels (r = −0.199, P < 0.05). ConclusionsDrug-naïve T2D patients with lower postprandial glucose concentration during CSII therapy exhibit better β-cell function recovery.