C-peptide is a substance released by the pancreas into the blood as a byproduct of the formation of insulin. This test measures the amount of C-peptide in a blood or urine sample.
Interpretation of the Results
- A high level of C-peptide generally indicates a high level of endogenous insulin production. This may be in response to a high blood glucose caused by glucose intake and/or insulin resistance.
- A high level of C-peptide is also seen with insulinomas and may be seen with low blood potassium, Cushing syndrome, and renal failure.
- When used for monitoring, decreasing levels of C-peptide in someone with an insulinoma indicate a response to treatment; levels that are increasing may indicate a tumor recurrence.
- A low level of C-peptide is associated with a low level of insulin production. This can occur when insufficient insulin is being produced by the beta cells, with diabetes for example, or when production is suppressed by treatment with exogenous insulin.
Keywords: C-peptide; insulin; endogenous insulin; glucose