A C-peptide test measures the level of this peptide in the body.Normal
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
The level of C-peptide in the blood must be read with the results of a blood glucose test. Both these tests will be done at the same time.C-peptide
- Fasting: 0.51–2.72 nanograms per milliliter (ng/mL) or 0.17–0.90 nanomoles per liter (nmol/L)
- High levels of both C-peptide and blood glucose are found in people with type 2 diabetes or insulin resistance (such as from Cushing's syndrome).
- A high level of C-peptide with a low blood glucose level may mean that an insulin-producing tumor of the pancreas (insulinoma) is present or that the use of certain medicines such as sulfonylureas (for example, glyburide) is causing the high level.
- If C-peptide levels are high after an insulinoma is taken out, it may mean that the tumor has returned or that the tumor has spread to other parts of the body (metastasized).
- Low levels of both C-peptide and blood glucose are found in liver disease, a severe infection, Addison's disease, or insulin therapy.
- A low level of C-peptide with a high blood glucose level is found in people with type 1 diabetes.
- Complete removal of the pancreas (pancreatectomy) causes a C-peptide level so low it cannot be measured. The blood glucose level will be high, and insulin will be needed in order for the person to survive.
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