Managing Diabetes Magazine - diabetes
Diabetes and C-Peptide Testing
What it is and what it shows your doctor
If you have diabetes, your body has problems with insulin. With type 1 diabetes, the pancreas no longer makes insulin. In type 2 diabetes, insulin does not work as it should. The pancreas may also create less insulin.
What is the c-peptide test?
C-peptide (a type of hormone) and insulin are linked when first made by the pancreas. The level of c-peptide in the body shows how much insulin the pancreas is making.
Why is it done?
A c-peptide test can:
- figure out if you have type 1 or type 2 diabetes.
- determine whether the pancreas is still making any insulin in those with type 1 diabetes.
- measure how well the pancreas is working. Glucose levels determine need for insulin in those with type 2 diabetes.
- find out if a pancreas or islet transplant has been successful. Does the new pancreas now produce insulin?
How is the test done?
The test is usually done using a blood sample taken from a vein. It is normally done in a fasting state (you may be asked not to eat beforehand) with a glucose level. When done two hours after a meal, it is called a postprandial c-peptide test. Since the test is sent to a larger central lab, results may take some time to come back.
What is a normal result?
C-peptide levels are generally anywhere from 0.5 to 2.0 nanograms per milliliter. (This can vary slightly depending on the lab.)
What if my level is high?
C-peptide levels can be higher in people who have:
- taken certain oral diabetes medications
- recently been diagnosed with type 2 diabetes
- had a pancreas transplant
- an insulin-producing tumor (insulinoma)
- kidney failure (since c-peptide is mainly removed from the body by the kidneys).
What if my level is low?
C-peptide levels can be lower in people who have:
- type 1 diabetes (where the level may be low or not be detected)
- had type 2 diabetes for a while
- or are treated with insulin therapy
C-peptide tests are not done routinely for all people who have diabetes. Having one can help you and your doctor to better understand your diabetes.
While effort is made to reflect accepted medical knowledge and practice, articles in Family Health Online should not be relied upon for the treatment or management of any specified medical problem or concern and Family Health accepts no liability for reliance on the articles. For proper diagnosis and care, you should always consult your family physician promptly. © Copyright 2019, Family Health Magazine, a special publication of the Edmonton Journal, a division of Postmedia Network Inc., 10006 - 101 Street, Edmonton, AB T5J 0S1 [DI_MDa10]