The clinical significance of normal c-peptide and insulin is mainly manifested in the fasting state, the pancreatic β-cells still survive the function of insulin secretion. The c-peptide is a peptide cleaved during insulin production. c-peptide is not affected by the injection of insulin, and changes in c-peptide better reflect the function of the pancreatic β-cells in patients receiving insulin therapy, so as to guide patients in adjusting the dosage of insulin or deciding whether or not to continue the treatment. c-peptide is normal, which generally indicates that the pancreatic β-cells still have the function of secreting insulin. Insulin is an endocrine hormone secreted by pancreatic β-cells. Its main role is to promote the synthesis and metabolism of substances, and in particular it plays a key role in maintaining blood glucose levels in the body. When analyzing the function of the pancreatic islets, it is often combined with a glucose tolerance test to look at the blood glucose after the glucose tolerance and the peaks of insulin and c-peptide. If insulin and c-peptide values are abnormal, seek medical attention.