Plasma C-peptide

Plasma C-peptide is a peptide released into the bloodstream during the cleavage of proinsulin into insulin, serving as a marker of endogenous insulin production. Its measurement is clinically significant for differentiating between type 1 and type 2 diabetes, as low levels indicate reduced insulin production typical of type 1 diabetes. Elevated C-peptide levels can also be associated with insulinomas, highlighting its role in diagnosing insulin-secreting tumours.