Diabetes mellitus is a metabolic disorder of multiple aetiology. Destruction of pancreatic beta cells, hyperglycaemia, and insulin deficiency cause type 1 diabetes mellitus. Diabetic nephropathy is the damage to kidneys because of diabetes. It is predominantly seen in patients with type 1 diabetes (insulin-dependent type) and type 2 diabetes (non-insulin-dependent type). An active peptide hormone, C-peptide has the likelihood of causing major physiological effects. C-peptide is the best indication of endogenous insulin secretion occurring in patients with diabetes. In this regard, the current study undertakes a comprehensive study of C-peptide and kidney (renal) failure in patients with diabetes mellitus in order to assess their association. A prospective cross sectional study is conducted at King Abdul Aziz University Hospital. The subjects for this study were patients with type 2 DM. Laboratory tests such as HbA1c, serum creatinine, urine albumin and creatinine, fasting serum C-peptide, and blood urea nitrogen are conducted. Data was analysed using analysis of variance (ANOVA) test to compare the values between different category patients. The study also found that there exists a significant mean difference between Cystacin C and C-peptide levels. However, the study has certain limitations. Firstly, the number of patients with elevated levels of serum C-peptide was very small, and hence, valid conclusions with respect to the association of serum C-peptide with renal parameters could not be discerned. Therefore, there is a need for further studies with more number of patients.