C-Peptide (SI)

Connecting Peptide of Insulin

Up to 24 hours

Electrochemiluminesence Immunoassay (ECLIA)

Results should be interpreted in the context of the clinical condition.

See overview

Accredited NRL Laboratory

Daily

C-peptide is a valuable clinical marker of endogenous insulin production, as it is co-secreted with insulin from pancreatic beta cells. Unlike insulin, C-peptide is not extracted by the liver and has a longer half-life, making it a reliable indicator of beta-cell function. It helps differentiate between type 1 and type 2 diabetes, evaluate suspected insulinoma, and assess residual beta-cell activity in patients on insulin therapy. In hypoglycemia, elevated C-peptide suggests endogenous hyperinsulinism, while low levels indicate exogenous insulin use. C-peptide is also used to monitor pancreatic function in patients undergoing islet transplantation or with longstanding diabetes.

Serum or Plasma (Li-Hep)

Minimum 0.5 mL

Serum Separator Tube (SST; Gold Top), Plain Tube (Red Top), Lithium Heparin Plasma (Green Top)

No special preparation is required for this test. You may eat, drink, and take your medications as normal, unless instructed otherwise by your healthcare provider.

Samples should be sent to the laboratory as soon as possible after collection. If this is not possible, samples should be centrifuged and transported refrigerated (2 to 8°C).