The progress of metabolic syndrome (MetS) continues with the onset of type-2 diabetes mellitus (Type-2 DM) along with linkage to other disorders such as neurodegenerative, especially Alzheimer's disease (AD), via oxidative stress and low grade systemic inflammatory process. Type-2 DM and AD are health disorders of priority research. The treatment for an individual suffering with Type- 2 DM and/or AD requires monitoring by clinicians. The aim of this study was to investigate the role of C-peptide and its correlation to insulin resistance, body mass index (BMI), β cell function, insulin sensitivity, lipid profile and hemoglobin A1c (HbA1c). The study was designed to include 96 Type-2 DM individuals from India. 58.3% males and 41.7% females were selected and fasting blood samples were collected for estimation of fasting C-peptide, fasting blood sugar (FBS), postprandial blood sugar (PPBS), HbA1c and lipid profile. Analysis was done on Hitachi912 and Elecsys 2010 using Roche reagents and standard controls. Anthropometries to calculate BMI and β cell function, insulin sensitivity, and insulin resistance were obtained. The statistical tool ANOVA, followed by calculation of p-value and r – value were applied for investigating correlation of C-peptide levels to those of high density lipoprotein-C (HDL-C), low density lipoprotein-C (LDL-C), triglycerides (TGL), HbA1c, β cell function, insulin sensitivity and insulin resistance. Highly significant positive correlations were observed in different quantiles of C-peptide levels to the studied parameters of MetS, BMI and % β cell function. Lower HDL-C level was found to be significantly related to higher C-peptide levels. Similarly, TGL and C-peptide levels displayed a significant positive correlation. A significant negative correlation was observed between C-peptide quantiles and % sensitivity. Thus, insulin resistance showed a positive correlation until the fourth quantile. No significant correlation was observed between C-peptide and HbA1c levels. This study demonstrates that assessment of C-peptide levels is a useful tool to monitor the progress of MetS among patients suffering from Type-2 DM and AD, as these disorders are intertwined to each other by common metabolic pathways. Assessment of C-peptide levels, along with HDL-C levels, in patients can be used to monitor insulin resistance.