Correlation of C-Peptide Levels With Complications of Type 2 Diabetes Mellitus

Introduction Type 2 diabetes (T2DM) is a major worldwide health issue that leads to serious problems in small and large blood vessels. C-peptide, which is released alongside insulin in equal quantities, acts as a reliable indicator of how well the beta cells of the pancreas are functioning and may be associated with diabetes-related complications. Methodology This one-year cross-sectional observational study took place at Baba Raghav Das Medical College in Gorakhpur, including 130 patients with type 2 diabetes who had had the condition for more than 10 years. Participants received thorough assessments for small blood vessel issues (such as retinopathy, nephropathy, and neuropathy) and large blood vessel problems (such as coronary artery disease and peripheral vascular disease) using standardized diagnostic criteria. Blood tests measured C-peptide levels, HbA1c, and other lab values. Statistical analysis was conducted using Python 3.12 with appropriate statistical libraries, employing t-tests for continuous variables, chi-square tests for categorical variables, and one-way ANOVA for multi-group comparisons. Results The study included 130 participants (n=130, mean age 59.4±12.0 years, 60% female) with a mean diabetes duration of 12.5±2.8 years and a mean HbA1c of 8.5±2.5%. Mean C-peptide level was 6.07±4.61 ng/mL. Microvascular complications showed age-related increases: retinopathy (25% in <45 years to 76.1% in >60 years), nephropathy (12.5% to 47.8%), and neuropathy (12.5% to 58.2%). Patients with complications demonstrated significantly lower C-peptide levels compared to those without complications (retinopathy: 5.29 vs 7.52 ng/mL, t=-2.37, p=0.0208; nephropathy: 4.87 vs 6.77 ng/mL, t=-2.58, p=0.0113; neuropathy: 4.59 vs 7.64 ng/mL, t=-4.12, p=0.0001). High C-peptide levels correlated with better glycemic control, with 48.2% achieving HbA1c <7.5% compared to only 10% in the low C-peptide group (χ²=8.45, p<0.05). Conclusion C-peptide levels demonstrate a significant inverse correlation with microvascular complications in T2DM patients. Lower C-peptide concentrations are associated with poorer glycemic control, higher complication rates, and increased insulin dependency, suggesting its potential utility as a biomarker for risk stratification and therapeutic decision-making.