Background: Diabetes mellitus refers to a group of common metabolic disorders that share the phenotype of hyperglycemia. It occurs either due to insulin deficiency or insulin resistance. It is an ongoing progressive disorder. The long term complications can be prevented by early screening of diabetes and initiating treatment. Progression of the disease is depicted in the form of worsening hyperglycemia, which may either be due to decreasing secretory activity of beta cells of pancreas or increasing insulin resistance, or in the form of progression of complications. The worldwide prevalence of diabetes mellitus has risen dramatically over the past two decades, from an estimated 30 million cases in 1985 to 415 million in 2017. Adding to this burden is the increasing incidence of type 2 diabetes mellitus. Hence, there is a need to understand the pathophysiology of diabetes, insulin secretion and insulin resistance and overcome them. One such way is to measure beta cell secretory activity. Measurement of C-peptide, which is secreted along with Insulin, provides a better index of endogenous insulin production and pancreatic beta cell function. Materials And Methods: It is a prospective interventional study done by simple random procedure, over a period of 18 months (1st March 2021 to 31st August 2022) with 200 cases. Results: Study reveals that there is no statistically significant difference of mean FBS with Quantile C-peptide levels. But there is statistically significant negative correlation between duration of diabetes and C-peptide levels in the study population (p<0.05). As duration of diabetes increases, C-peptide value decreases. And, there was statistically highly significant positive correlation between BMI and C-peptide levels in the study population (p<0.001). As BMI value increases, C-peptide level also increases. Conclusion: This study suggests that BMI and duration of diabetes are major factors in ß cell function in people with diabetes.