Background: Diabetes Mellitusincluding both Type 1 and Type 2 diabetes, is a global health challenge with rising prevalence. Diabetic nephropathy, a major complication of diabetes, is a leading cause of chronic kidney disease and end-stage renal disease ESRD. Understanding the relationship between renal function markers, Glycemic control and the duration of diabetes is crucial for effective management and prevention of renal complications. Aim: This study aims to investigate the correlation between serum creatinine, blood urea levels, glycemic index and the duration of diabetes in patients with T1 DM and T2 DM at a tertiary healthcare center. Methods: A cross-sectional comparative study was conducted on 200 diabetic patients (100 with Type 1 diabetes and 100 with Type 2 diabetes) at MGM Medical College Hospital, Jamshedpur, from April 2022 to July 2023. Serum creatinine, blood urea, Glycemic Index and duration of diabetes were assessed. Data were analyzed using SPSS version 23.0, with correlation and regression analyses performed to evaluate relationships between variables. Results: The study found significant correlations between Serum creatinine, blood urea levels, Glycemic index, and the duration of diabetes in both T1 and T2 diabetes groups. Patients with T2 diabetes had higher Serum creatinine and blood urea levels compared to those with T1 diabetes. Regression analysis identified Glycemic index and duration of diabetes as significant predictors of renal function markers. Conclusion: The study highlights a strong relation between poor Glycemic control longer diabetes duration, and deteriorating renal function in diabetic patients. Type 2 diabetes patients, in particular, are at greater risk of renal complications. Early intervention and continuous monitoring of renal function, alongside Glycemic control are essential to prevent the progression of diabetic nephropathy. Recommendations: To mitigate the risk of diabetic nephropathy, it is recommended that healthcare providers focus on strict Glycemic control particularly in patients with longer diabetes duration. Regular monitoring of renal function markers should be integrated into diabetes management protocols to identify at-risk individuals early and tailor interventions accordingly.