L-SelenoMethionine is a major natural food-form of selenium. Target： The median lethal dose (LD50) of L-SelenoMethionine in rats given an intraperitoneal injection was determined to 4.25 mg Se/kg body and thus is comparable to that of selenite or selenate. In mice, the LD50 of L-SelenoMethionine was 8.8 ± 1.37 mg Se/kg, and the minimal lethal dose, 4.0 mg Se/kg, after intravenous injection.