C-Peptide

Description: A C-peptide test is a test that will measure the amount of C-peptide, a short amino acid chain, in the blood. This test can be used to determine if the beta cells in the pancreas are producing enough insulin. It can also be used to evaluate the reason for low blood glucose.

Also Known As: Insulin C-Peptide Test, Connecting Peptide Insulin Test, Proinsulin C-peptide test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: Fasting is required.

When is a C-Peptide test ordered?

When a person is initially diagnosed with type 1 diabetes, C-peptide levels may be ordered as part of a "residual beta cell function" study.

When a person has type 2 diabetes, a health practitioner may request the test on a regular basis to track the state of their beta cells and insulin production over time and assess whether or not insulin injections are needed.

When there is reported acute or recurring low blood glucose and/or excess insulin is suspected, C-peptide levels can be measured.

A C-peptide test may be conducted on a regular basis after a person has been diagnosed with an insulinoma to assess treatment effectiveness and detect tumor recurrence.

When a person's pancreas has been removed or has had pancreas islet cell transplants, C-peptide levels may be tracked over time.

What does a C-Peptide blood test check for?

C-peptide is a chemical made up of a short chain of amino acids that is released into the bloodstream as a byproduct of the pancreas producing insulin. This test determines how much C-peptide is present in a blood or urine sample.

Proinsulin, a physiologically inactive molecule, splits apart in the pancreas, within specialized cells called beta cells, to generate one molecule of C-peptide and one molecule of insulin. Insulin is necessary on a regular basis for the transport of glucose into the body's cells. When insulin is needed and released into the bloodstream in reaction to elevated glucose levels, equal amounts of C-peptide are also released. C-peptide can be used as a measure of insulin production because it is produced at the same rate as insulin.

C-peptide testing, in instance, can be used to assess the body's insulin production and distinguish it from insulin that is not produced by the body but is given as diabetes medication and hence does not generate C-peptide. This test can be done in conjunction with a blood test for insulin.

Lab tests often ordered with a C-Peptide test:

Conditions where a C-Peptide test is recommended:

How does my health care provider use a C-Peptide test?

C-peptide testing can be used for a variety of reasons. When proinsulin breaks into one molecule of C-peptide and one molecule of insulin, C-peptide is created by the beta cells in the pancreas. Insulin is a hormone that allows the body to use glucose as its primary energy source. C-peptide is a helpful measure of insulin production since it is produced at the same rate as insulin.

A C-peptide test is not used to diagnose diabetes; however, when a person is newly diagnosed with diabetes, it may be ordered alone or in conjunction with an insulin level to evaluate how much insulin the pancreas is currently making.

The body becomes resistant to the effects of insulin in type 2 diabetes, so it compensates by manufacturing and releasing more insulin, which can destroy beta cells. Oral medications are commonly used to help type 2 diabetics stimulate their bodies to produce more insulin and/or make their cells more receptive to the insulin that is already produced. Type 2 diabetics may eventually produce very little insulin as a result of beta cell loss, necessitating insulin injections. Because any insulin produced by the body is reflected in the C-peptide level, the C-peptide test can be used to track beta cell activity and capability over time and to assist a health care provider in deciding when to start insulin treatment.

Antibodies to insulin can develop in people on insulin therapy, independent of the source of the insulin. These often interfere with insulin assays, making it difficult to assess endogenous insulin production directly. C-peptide measurement is a good alternative to insulin testing in certain situations.

C-peptide levels can also be utilized in conjunction with insulin and glucose levels to help determine the source of hypoglycemia and track its therapy. Excessive insulin supplementation, alcohol intake, hereditary liver enzyme deficits, liver or kidney illness, or insulinomas can all cause hypoglycemia symptoms.

Insulinomas can be diagnosed with the C-peptide test. These are tumors of the pancreas' islet cells, which can produce excessive levels of insulin and C-peptide, resulting in abrupt hypoglycemia. C-peptide testing can be used to track how well insulinoma treatment is working and to detect recurrence.

A C-peptide test may be performed to help evaluate a person who has been diagnosed with metabolic syndrome, a group of risk factors that includes abdominal obesity, high blood pressure, and elevated blood glucose and/or insulin resistance.

C-peptide levels are occasionally used to verify the effectiveness of treatment and the procedure's sustained success after someone has had his pancreatic removed or has had pancreas islet cell transplants to restore the ability to manufacture insulin.

What do my C-Peptide test results mean?

A high level of C-peptide implies that endogenous insulin synthesis is high. This could be a result of a high blood glucose level brought on by carbohydrate consumption and/or insulin resistance. Insulinomas, low blood potassium, Cushing syndrome, and renal failure are all linked to a high level of C-peptide.

C-peptide levels that are decreasing in someone with an insulinoma suggest a response to treatment when used for monitoring; levels that are increasing may indicate a tumor recurrence when used for monitoring.

A low amount of C-peptide is linked to a reduction in insulin synthesis. This can happen when the beta cells generate insufficient insulin, as in diabetes, or when their production is reduced by exogenous insulin administration.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.