C-Peptide

C-Peptide (Connecting Peptide) is released from the pancreas in equal amounts with insulin when proinsulin is cleaved. Measuring C-peptide reflects endogenous insulin production by the pancreatic beta cells. It is useful for differentiating between type 1 diabetes (low/absent C-peptide) and type 2 diabetes (often normal or high C-peptide initially, indicating insulin resistance), and for assessing beta-cell function or presence of insulinoma (high C-peptide). Assumes fasting sample.