what is c peptide
C-peptide testing can be used for a few different purposes. C-peptide is a substance produced by the beta cells in the pancreas when proinsulin splits apart and forms one molecule of C-peptide and one molecule of insulin. Insulin is the hormone that is vital for the body to use its main energy source, glucose. A C-peptide test is not ordered to help diagnose diabetes, but when a person has been newly diagnosed with diabetes, it may be ordered by itself or along with an insulin level to help determine how much insulin a person's pancreas is still producing (endogenous insulin).