The increase in number of diabetic patients motivated scientists to find new methods to control such disease. In the present study, the action of Garlic [Allium sativum] was studied on normal and sterptozocin [STZ]-induced diabetic rats. Experimental group included 60 male albino rats divided equally into control group, control group given oral daily dose of garlic [100 mg/kg B.wt] for 16 weeks, STZ-induced diabetic untreated group, and diabetic garlic-treated group included STZ-induced diabetic rats given the daily oral dose of the garlic for 16 weeks. Blood samples were collected for determination of blood glucose, nitric oxide [NO], malondialdehyde [MDA], and lipid profile [triglycerides [TG], cholesterol [C], high density lipoprotein-cholesterol [HDL-C], and low density lipoprotein-cholesterol [LDL-C]].Supplementation of garlic to non-diabetic rats had produced no significant differences as regards any of the parameters including glucose, lipid profile, nitric oxide, and lipid peroxidation end product malondialdehyde [MDA] levels when compared with the control group. The diabetic rats showed significant elevation in serum glucose, NO, MDA, TG, C, and LDL-C. Concomitantly significant decrease in HDL-C was detected when compared with their corresponding values of controls. However, supplementation of garlic to the diabetic rats had shown a significant decrease in serum glucose, TG, C, LDL-C, NO, [and MDA] levels, while elevation in HDL-C level was detected. Thus, from the present study it is assumed that garlic treatment decrease the blood glucose level. Antioxidant garlic may protect B cells against toxic effect of ROS [reactive oxygen species] provoked due to hyperglycemia. This was indicated by the significant decrease of oxidative stress after garlic treatment in the studied group. It is concluded that garlic supplementation improves blood lipid profiles, strengthens blood oxidant potential, and causes significant reduction in blood glucose; NO; and MDA levels. These results suggest that garlic exerted antioxidant and antihyperglycemic effects.