C-Peptide
Definition
C-peptide is an amino acid chain formed during the pancreas's production of insulin.
Purpose
Because it stays in the blood longer than insulin and is not affected by insulin given from outside the body, it is used to measure the body's own insulin production. Uses include:
- Investigating the cause of hypoglycemia (low blood sugar)
- Monitoring how much insulin the pancreas is producing in a patient on insulin therapy
- Monitoring treatment of an insulinoma (an insulin-secreting tumor)
- Distinguishing type 1 from type 2 diabetes when the diagnosis is unclear
Results
| Result | What it may suggest |
|---|---|
| High | Type 2 diabetes, Cushing syndrome, insulinoma, kidney failure, low potassium |
| Low | Type 1 diabetes, insulin overdose, severe infection, Addison disease, liver disease |
Normal Values
Specific to the laboratory.
Risks and Limitations
The test alone cannot diagnose diabetes. Fasting for 8 to 12 hours is required; it is run on blood or a 24-hour urine sample.