C-Peptide - serum

Last updated: Monday, 06, August, 2007

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Item Process

5 mL blood in plain tube.



Reference Interval

Fasting: 0.8-1.9 µg/L.


To assess pancreatic beta cell function and to distinguish type 1 from type 2 diabetes.

Investigation of hypoglycaemia thought to be due to hyperinsulinism, particularly if surreptitious use of insulin is suspected.


Pancreatic beta cells secrete C-peptide with insulin, so levels decline with beta cell failure.

Inappropriately high levels of insulin and C-peptide during hypoglycaemia indicate endogenous hyperinsulinism.

Inappropriately high levels of insulin with low C-peptide during hypoglycaemia indicate exogenous hyperinsulinism.


Cryer PE. In: Wilson JD and Foster DW eds. Williams Textbook of Endocrinology. 8th ed. WB Saunders 1992.