C-peptide

Keywords: C-peptide, Insulin C-peptide

Specimen:

5 mL blood in plain tube.

Method:

Immunoassay.

Reference Interval:

Fasting: 0.8-1.9 µg/L.

Application:

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.

Interpretation:

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.

Reference:

Cryer PE. In: Wilson JD, Foster DW, eds. Williams Textbook of Endocrinology. 10th ed. Philadelphia: WB Saunders, 2003.