C-Peptide is useful in the evaluation of pancreatic beta cell function (e.g., helping distinguish type 1 from type 2 diabetes mellitus, or monitoring patients who have received islet cell or pancreatic transplant) and for determining the source of insulin in patients with hyperinsulinemic hypoglycemia (e.g., distinguishing insulin-secreting tumors from exogenous insulin administration). It is also sometimes measured as an additional means (more resistant to hemolysis than is insulin itself) for evaluating glucose tolerance tests.
Patients should fast 12 hours prior to collection
Draw fasting specimen. Administer oral glucose solution
(1.75 g/kg body weight or 75 g maximum). Collect 1 mL serum
for each timed specimen post glucose dose. All tubes must be
clearly marked with time drawn. Submit all tubes with one test
Reference ranges available: Fasting, 30, 60, 90, 120, 150,
180, 240 and 300 minutes post glucose.