c-peptide-test
Reviewed
This test measures the level of C-peptide in your blood or urine. C-peptide is released by the pancreas at the same time and in equal amounts as insulin, but it stays in the blood longer and is not affected by insulin from diabetes medicines. Therefore, the test shows how much insulin your body is making naturally.
Preparation and collection
For a blood test, you may need to fast (not eat or drink) for 8–12 hours before the test. Your provider may also want to test C-peptide after you have eaten. Ask your provider for specific instructions for either a blood or urine test.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- A C-peptide test is not used to diagnose diabetes. Other tests, such as blood glucose and urine glucose, are used to screen for and diagnose diabetes.
- Results must be interpreted by a healthcare professional based on your age, health, medicines, and other test results.
What to do next
If you have questions about your results, talk with your provider.