What is C-Peptide?
C-peptide is a short chain of amino acids which is released by the pancreas into the blood as a by-product of the formation of insulin. This test measures the amount of C-peptide in a blood sample.
Why is C-Peptide done?
The C-peptide test should be performed:
· To help evaluate insulin production by the beta cells in the pancreas
· To help determine the cause of low blood sugar (hypoglycemia) whether it is due to insulin-producing tumors in the body or due to insulin injections (medicinal insulin)
· To monitor how well the insulinomas (tumors) are responding to the treatment: Decreasing levels of C-peptide in someone with an insulinoma indicate a response to treatment; levels that are increasing may indicate a tumor recurrence
· To distinguish between type I and type II diabetes mellitus
· To help evaluate a person diagnosed with metabolic syndrome (set of abdominal obesity, increased blood glucose and/or insulin resistance, abnormal blood lipid levels, and high blood pressure)
· After pancreatic transplantation: In case of pancreatic islet cell transplants, intended to restore the ability to make insulin, C-peptide levels may be used to verify the effectiveness of treatment and continued success of the procedure.
What does C-Peptide Measure?
C-peptide is a short chain of amino acids released into the blood as a by-product of insulin production. This test measures the amount of C-peptide in blood and helps evaluate the production of insulin made by the body (endogenous). This helps in differentiating endogenous insulin from the insulin that is not produced by the body but is taken in as diabetic medication (exogenous). This is possible because the insulin that is taken in as diabetic medications does not generate C-peptide.
Beta cells of the pancreas produce proinsulin which is a biologically inactive molecule. This molecule splits apart to form one molecule of C-peptide and one molecule of insulin. The uptake, utilization, and storage of glucose after it is absorbed in the intestines is facilitated by the hormone called insulin. When insulin is released from the beta cells into the blood in response to increased levels of glucose, equal amounts of C-peptides are also released. Since C-peptide is produced at the same rate as insulin, it is useful as a marker of insulin production.
Interpreting C-Peptide results
Normal reference range:
C-peptide (fasting): 0.81-3.85 ng/mL
Note: In normal individuals, the molar ratio of C-peptide to insulin in the fasting state is 5:1
· A high level of C-peptide generally indicates a high level of endogenous insulin production which may be in response to high blood glucose levels caused by glucose intake or insulin resistance.
· High levels of C-peptide are also seen with insulinomas.
· High levels of C-peptide may be seen with low blood potassium, Cushing syndrome, and renal failure.
Low levels: A low level of C-peptide indicates a low level of insulin production by the beta cells that can be seen in diabetes or when production is suppressed by treatment with exogenous insulin.
Answers to Patient Concerns & Frequently Asked Questions (FAQs) about C-Peptide
Frequently Asked Questions about C-Peptide