One of the most common causes of dialysis is diabetic nephropathy (DN), which can be prevented or delayed with early identification. When it comes to chronic kidney disease (CKD) and type 2 diabetes, little is known about the renal function marker serum cystatin C (sCysC) and its link to glomerular filtration rate. In this study, we tested the efficacy of sCysC as a marker of early DN and CKD in patients from the southern Indian coastal region.