C-Peptide Test Test
The C-peptide test measures how much insulin your body is making naturally. It helps find the cause of low blood sugar, manage diabetes treatment, and check for a rare pancreas tumor called an insulinoma.
What this test measures
This test measures the level of C-peptide in your blood or urine. C-peptide is a substance your pancreas makes at the same time and in equal amounts as insulin. Because C-peptide stays in your blood longer and is not affected by insulin medicines, it gives an accurate picture of how much insulin your body is making naturally.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
A high level of C-peptide usually means your body is making too much insulin. Conditions that can cause this include type 2 diabetes, Cushing's syndrome, insulinoma (a pancreas tumor), kidney failure, or low potassium in your blood.
Lower-than-normal results
A low level of C-peptide may mean your body isn't making enough insulin. Conditions that can cause this include type 1 diabetes, some cases of type 2 diabetes, taking too much insulin for diabetes, a severe infection, Addison disease, or liver disease.
Frequently asked questions
What is a C-peptide test?
It measures the level of C-peptide in your blood or urine to see how much insulin your body is making naturally.
Why would I need a C-peptide test?
To find the cause of low blood sugar, manage diabetes treatment, or check for a rare pancreas tumor called an insulinoma.
How is C-peptide different from insulin?
C-peptide and insulin are released together, but C-peptide stays in your blood longer and is not affected by insulin medicines, so it gives a more accurate picture of your natural insulin production.
What does a high C-peptide level mean?
It usually means your body is making too much insulin. This can happen with type 2 diabetes, Cushing's syndrome, insulinoma, kidney failure, or low potassium.
What does a low C-peptide level mean?
It may mean your body isn't making enough insulin. This can happen with type 1 diabetes, some cases of type 2 diabetes, taking too much insulin, severe infection, Addison disease, or liver disease.
Related lab tests
Sources
- MedlinePlus: C-Peptide Test — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.