C-peptide testing

A c-peptide test will detect how much insulin your body is producing. The test is useful to determine whether you have Type 1 Diabetes or Type 2 Diabetes and whether you have insulin resistance.

What is C-peptide?

C-peptide is released at the same time as insulin is produced. In each molecule of insulin there exists a molecule of C-peptide. C-peptide itself will not affect blood sugar levels.

C-peptide is an effective measurement for insulin production because C-peptide tends to stay longer in the body than insulin.

Why the test is used?

To distinguish whether you have Type 1 or Type 2 Diabetes

To confirm whether you have insulin resistance

To find out the causes of hypoglycemia (low blood sugar)

To monitor insulin production after removal of pancreatic tumors

How is C-peptide test performed?

A fasting blood glucose test will be done to measure C-peptide readings.

You will need to fast for 8-12 hours before the test is done.

If you are on hypoglycemic medicines, you may need to stop taking those medicines before the test.

During the test, a blood sample will be taken from your arm. Levels of both c-peptide and blood glucose will be measured.

C-peptide test results

Normal range for c-peptide is 0.51 to 2.72 nanograms per millilitre(ng/mL).

Low c-peptide level and high blood glucose is an indicator for Type 1 Diabetes.

Low levels of both c-peptide and blood glucose may indicate liver disease, serious infection or Addison’s disease.

In comparison, high c-peptide and lowered blood glucose are signs for insulin resistance, which can be signs for Type 2 Diabetes and Cushing’s Syndrome.

High c-peptide and low blood glucose may result from insulinoma (pancreatic tumor) unless hypoglycemic medicines have affected the result.