Aim: Role of serum magnesium levels in type 2 diabetes mellitus patients. Methods: The present Prospective study was conducted among total of 100 patients of type 2 DM, and 100 nondiabetic controls, Type 2 diabetes mellitus patients aged >18 years were included in the study. Patients with type 1 Diabetes Mellitus, History of nephritic syndrome or renal disease predating type 2 DM diagnosis, alcohol dependence, UTI/Pyelonephritis. Results: The mean sample population period of diabetes was 7.65 years, ranging from 0 to 30 years. 70 Patients received only oral hypoglycaemic agents and insulin was given to 30 patients. Hypertension was seen in 45 patients, 31 patients had a stroke, 20 had ischemic heart disease. There were a total of 57 patients with diabetic nephropathy, 27 patients with diabetic retinopathy, and 16 patients with diabetic neuropathy. There was a marked change in serum magnesium levels between diabetics and controls. The mean serum magnesium concentrations were 1.92 mg/dL and 2.21 mg/dL respectively for cases and controls. Cases were 40 times more likely to have hypomagnesemia (< 1.82 mg/dL) than controls with p<0.001. Among cases 45 patients (45%) had hypomagnesemia, 55 patients had normomagnesemia, and no patient had hypermagnesemia. Among controls 3 patient had hypomagnesemia, 97 patients had normomagnesemia. Among cases 55.56% males and 44.44% females were hypomagnesemic, males were more likely to have hypomagnesemia, with significant p value 0.003<0.05. There was a disparity between regulated and uncontrolled diabetes levels of magnesium. The average serum magnesium levels were 1.97 mg/dL and 1.80 mg/dL respectively among controlled and uncontrolled diabetics. However P value was not significant 0.119>0.05. Average serum creatinine levels were 1.31 mg/dL and 0.89 mg/dL, respectively, amongst cases and controls. The mean FBS values were 168.15 mg/dL and 98.79 mg/dL, respectively, among cases and controls. Conclusion: We concluded that the Retinopathy, neuropathy and nephropathy are significantly associated with hypomagnesemia. Hypomagnesemia prevalence was elevated in patients with HbA1c>7%. Males had hypomagnesemia more commonly. No significant correlation with other parameters was identified.