L-carnitine is an essential quarternary amine having an important role in the P-oxidation of fatty acids. Although L-carnitine was shown to be protective against toxic effects of some chemicals the dose-effect relationship with respect to its antioxidant action and protection from lipid peroxidation is unknown. To evaluate the dose-response profile of L-carnitine on blood sialic acid, glutathione and malondialdehyde concentrations, 40 mice were randomly allocated to 4 groups. Experimental mice were treated with intraperitoneal saline for 5 days (Group 1), L-carnitine at 100 mg/kg for 5 days (Group 2), L-carnitine at 250 mg/kg for 5 days (Group 3), L-carnitine at 500 mg/kg for 5 days (Group 4). Following the treatments, blood samples were collected, and blood glutathione, malondialdehyde and sialic acid concentrations were determined. L-carnitine provided an antioxidant action at doses of 100, 250 and 500 mg/kg with the strongest antioxidant action observed at 500 mg/kg dose. There was a significant increase in malondialdehyde and sialic acid concentrations at all doses of L-carnitine with the highest effect seen at 500 mg/kg dose. In addition, L-carnitine caused a dose-dependent elevation in glutathione level.