Diabetes is accumulation of higher glucose content in the blood. When the glucose level is increased it indicates the low insulin secretion or no response to the insulin production in the body. C-peptide is cleaved from the proinsulin chains A and B during insulin synthesis. C- peptide produced in the same amount toinsulin because; C-peptide is removed when insulin is formed. As per the amount is same for both the Cpeptide and insulin, the C-peptide works as a biomarker for finding the insulin secretion and to finding of diabetes type accurately. In this review it has been focused on C-peptide and its role as a biomarker in diabetes and predictor of complications and other risks caused by the diabetes.