C-peptide

C-peptide is a small protein that is produced when the body makes insulin, the hormone that helps regulate blood sugar. When the pancreas creates insulin, it initially forms a larger molecule called proinsulin, which then splits into two parts: active insulin and C-peptide. Measuring C-peptide levels helps doctors assess how much insulin the body is producing, especially useful for diagnosing and managing diabetes. Since C-peptide stays in the blood longer than insulin and isn't affected by insulin injections, it provides a reliable indicator of the body's own insulin production.