In this study, the effects of magnesium (Mg) and L-carnitine on body weight, blood glucose, plasma lipase and paraoxonase activities, serum lipids, lipid peroxidation (MDA) and total antioxidant capacity (TAC) were determined in rats with experimental diabetes mellitus induced by streptozotocin. Eighty Wistar albino male rats (200-250 g) were divided into eight groups of ten. First group (control) received 2 ml distilled water; group 2 received 50 mg/kg (b.w., i.p.) STZ; Group 3 received 125 mg/kg (b.w.) Mg; group 4 received 300 mg/kg (b.w.) L-carnitine; group 5 received 125 mg/kg (b.w.) Mg+300 mg/kg (b.w.) L-carnitine; group 6 received 50 mg/kg (b.w.) STZ+125 mg/kg (b.w.) Mg; Group 7 received 50 mg/kg (b.w.) STZ+300 mg/kg (b.w.) L-carnitine; Group 8 received 50 mg/kg (b.w.) STZ+125 mg/kg (b.w.) Mg+300 mg/kg (b.w.) L-carnitine for four weeks. In rats with diabetes, oral administration of 125 mg/kg Mg and 300 mg/kg L-carnitine separately, was found to have no effect on body weight, blood glucose, serum total cholesterol, HDL and LDL-cholesterol and TAC. In diabetic rats, serum MDA levels decreased with the administration of both substances separately and/or in combination, and triglyceride levels decreased with only L-carnitine and Mg+L-carnitine administration. Especially with the combined application of Mg and L-carnitine, the high blood glucose levels determined in rats with diabetes decreased significantly. As a result, it was concluded that Mg and L-carnitine may have antidiabetic effects, especially in combination.