C-peptide, a 31-amino-acid connecting peptide released with insulin, is a gold-standard biomarker for assessing endogenous insulin secretion and pancreatic β-cell function. Unlike insulin, it is not subject to hepatic clearance, making it highly reliable for diabetes diagnostics and research. Recent clinical studies highlight C-peptide as a validated surrogate endpoint in type 1 diabetes trials, strongly correlating with HbA1c levels and long-term metabolic outcomes. Catalina’s high-quality C-peptide antibodies are precise, reproducible tools for advancing studies in diabetes pathogenesis, β-cell preservation, and disease-modifying therapy development.