This test measures the amount of C-peptide in the blood. C-peptide is a chain of amino acids that enters the blood as a by-product of insulin formation.
Read more about the C-peptide blood test.
C-peptide and insulin are produced in the pancreas at the same rate and released in to the bloodstream in equal amounts when insulin is required in response to increased glucose levels. C-peptide stays in the bloodstream longer than insulin, making it a useful marker of insulin production.