It is not good to have a C-peptide that is too high or too low two hours after a meal; it is more appropriate to be within the normal range. C-peptide is secreted by human pancreatic islet β-cells and comes from a common precursor with insulin, so C-peptide levels are commonly used clinically to reflect endogenous insulin secretion. Under normal circumstances, the reference value of C-peptide is 0.3~1.3mmol/L during fasting, and C-peptide peaks around 0.5~1 hour after meal, which should be about 5~6 times of fasting. If the C-peptide level is too high, it may indicate the presence of insulin resistance, early type 2 diabetes, pancreatic islet β-cell tumor, etc.; if the C-peptide level is too low, it may indicate the presence of type 1 diabetes, type 2 diabetes, advanced diabetes. Therefore, it is recommended to consult a doctor for standardized diagnosis and treatment when necessary.