This two-part webcast offers a forward-looking view on how to both measure and modify the course of type 1 diabetes. In the opening presentation, our experts examine C-peptide as a sensitive surrogate marker of residual beta cell function - exploring its physiology, practical testing strategies across the T1D continuum, and growing evidence that even very low C-peptide levels are linked to fewer complications, less hypoglycaemia, and improved long-term outcomes. A complementary second talk outlines how novel immunotherapies and precision approaches aim to preserve beta cell function from the earliest disease stages, potentially redefining what “successful” management looks like. Together, these presentations connect cutting-edge biomarker science with emerging therapeutic paradigms.