In the context of diabetes or hypoglycemia, a measurement of C-peptide blood serum levels can be used to distinguish between different conditions with similar clinical features.

In the insulin synthesis pathway, first preproinsulin is translocated into the endoplasmic reticulum of beta cells of the pancreas with an A-chain, a C-peptide, a B-chain, and a signal sequence.

After proinsulin is packaged into vesicles in the Golgi apparatus (beta-granules), the C-peptide is removed, leaving the A-chain and B-chain bound together by disulfide bonds, that constitute the insulin molecule.

Equimolar amounts of C-peptide and insulin are then stored in secretory granules of the pancreatic beta cells and both are eventually released to the portal circulation.

[5] C-peptide has been shown to bind to the surface of a number of cell types such as neuronal, endothelial, fibroblast and renal tubular, at nanomolar concentrations to a receptor that is likely G-protein-coupled.

In vivo studies in animal models of type 1 diabetes have established that C-peptide administration results in significant improvements in nerve and kidney function.

[20] Studies have demonstrated that the presence of residual C-peptide in longstanding type-1 diabetes is associated with a lower risk for developing microvascular complications and a significant reduction in incidence of severe hypoglycaemia.