C-Peptide – plasma

Diagnostic Use

C-peptide represents the connecting peptide which is cleaved from proinsulin in the production of endogenous insulin. As such, the presence of C-peptide indicates endogenous production of insulin, whereas C-peptide is absent if only exogenous insulin is administered. For accurate interpretation in appropriate clinical settings, plasma C-peptide should be paired with laboratory plasma glucose (┬▒ insulin) testing. Depending on the clinical question, either fasting or non-fasting specimens may be appropriate.

In patients with diabetes, C-peptide may be of value in the assessment of residual pancreatic function in insulin treated diabetics, differentiating between types of diabetes (eg in presence of high or normal glucose, C-peptide is typically low or low-normal in Type 1 diabetes, but typically high in MODY or Type 2 diabetes).

In patients with hypoglycaemia, high C-peptide may be associated with insulinoma, dumping syndrome or sulphonylurea use, whereas low C-peptide is an appropriate physiological response representing less release of endogenous insulin. A 72 hour fast or mixed meal test may be performed in certain settings to provoke hypoglycaemia for this purpose and aid clinical diagnosis if it is not captured opportunistically.

It is suggested that an endocrinologist be consulted for further advice regarding interpretation.


Endo/Steroid Lab

Delphic Registration Code


Turnaround Time

7 days

Test Code