This study was performed to determine how the magnesium supplementation for a 4-week period affects the glucose and insulin levels at rest and at exhaustion in sportsmen. This is a 4 week study performed on 30 healthy male subjects varying between 18-22 ages. Subjects were separated into 3 groups. 1st group; group supplemented with magnesium, 2nd group; Magnesium supplementations exercise group, 3rd group; training group. Glucose and insulin parameters of the groups were measured 4 times; at rest and exhaustion in the beginning of the research and at rest and exhaustion after the end of 4 weeks application period. Glucose levels in exhaustion measurements both before and after the supplementation significantly increased compared to resting levels (p<0.05). Significant difference was determined in the glucose values of 1st and 2nd groups supplemented with magnesium in comparison to their first measurements (p<0.05). Insulin values a decrease in all of the 3 groups occurred with exercise both before and after the supplementation (p<0.05). Magnesium supplementation has an important effect on glucose levels whereas it has no effect on insulin levels.