This cross-sectional analytical study was carried out to observe serum magnesium in type 2 diabetes mellitus patients and was performed in the department of Physiology, Mymensingh Medical College, Mymensingh, Bangladesh from January 2016 to December 2016. For this purpose, a total number of 200 subjects of both sexes with age ranged from 30-60 years were selected of whom 100 were type 2 diabetic person and 100 were apparently healthy. Serum magnesium was significantly lower (p<0.0001) in both male and female of the study group in comparison to healthy control group. From this study, it may conclude that type 2 persons are considered to have significant positive relation for formation of hypomagnesaemia. So, prevention of type 2 diabetes mellitus by taking necessary steps like regular physical exercise, intake of healthy diet and behavior therapy may supplementation of magnesium help in prevention of type 2 diabetes mellitus related complication.