Magnesium supplementation has recently attracted attention as effective in the management of diabetes and its related complications though its mechanisms of action is yet to be fully unraveled. This study was carried out to determine the effects of magnesium supplementation on body weight, fasting blood sugar, Oral glucose tolerance (OGTT 2 and OGTT 4), glucose transporter isoform 2 (GLUT2), GLUT4 and insulin receptor (INSR) mRNA expressions in streptozotocin-nicotinamide induced diabetic Sprague dawley rats. A total of 24 Sprague dawley rats (Four groups of six rats each) were used for this study, and the treatment was for 28 days. Group 1: Normal control rats were given distilled water; Group 2: Metformin treated rats were given 100 mg/kg body weight; Group 3: Metformin + Magnesium treated rats were given 100 mg/kg and 1000 mg/kg body weight respectively; Group 4: Diabetic untreated rats given distilled water. Data were analyzed statistically using Analysis of Variance (ANOVA) and graphically by Graph pad prism. The GLUT4 and INSR gene expressions of Group 3 were significantly (p<0.05) upregulated when compared with Group 4. There was significant (p<0.05) decrease fasting blood sugar and GLUT2 mRNA level in the treated diabetic rats but the metformin-magnesium supplement treated group showed more decrease (p<0.05) when compared with the group treated with metformin only. This study demonstrates that magnesium may mediate effective metabolic control by stimulating insulin sensitivity, and upregulating mRNA levels of GLUT4, INSR as well as improving glucose tolerance in diabetic rats. Therefore, magnesium supplementation appears to have a beneficial role and improves glucose uptake by cells in those at high risks of diabetes. Magnesium supplementation, Metformin, INSR, GLU4, glucose tolerance.