C-Peptide, Serum

The C-peptide test measures levels of the protein fragment C-peptide in the blood, generally found in equal amounts to insulin. Therefore, the level of C-peptide estimates how much insulin is being made in the body. Insulin is a hormone that helps the body use and control glucose levels.

The C-peptide test can be used to indicate a number of diseases and disorders but the primary use in the diagnosis of hypoglycemia (low blood sugar). C-peptide levels can also be used to establish whether Type 1 diabetes or Type 2 diabetes is present. An individual with Type 1 diabetes has a low level of insulin and C-peptide. An individual with Type 2 diabetes has normal to high levels of C-peptide and insulin.