It is not normal for two-hour postprandial C-peptide to be more than twice as much as fasting C-peptide. It is considered that two-hour postprandial C-peptide is low, and prompt medical attention is recommended. C-peptide is a peptide cleaved during the production of insulin. It has a longer half-life than insulin (about 35 minutes), is not inactivated by hepatic enzymes, and is degraded only in the kidneys, and partly excreted from the urine in its original form. The blood C-peptide concentration is not interfered by exogenous insulin or anti-insulin antibodies, and can more accurately reflect the function of pancreatic β-cells. In general, the C-peptide level two hours after a meal should be five to six times the C-peptide level in the fasting state, so the two-hour postprandial C-peptide is more than twice the fasting C-peptide consider the two-hour postprandial C-peptide low. If C-peptide is more than twice as high as fasting C-peptide, it is recommended to go to the hospital and ask the doctor to make a judgment, rather than making a blind judgment on your own.