Context: Therapeutic effects of alpha-L-guluronic acid with the greatest tolerability and efficacy (G2013) have been shown in experimental model of multiple sclerosis and other in vitro and in vivo examinations regarding alpha-L-guluronic acid; there are no toxicological researches on its safety although the pharmacological impacts have been recorded. Objective: This study was designed to determine the acute and sub chronic toxicity of alpha-L-guluronic acid in healthy male and female BALB/c mice. Materials and methods: For the acute toxicity study, the animals orally received five different single doses of alpha-L-guluronic acid and were kept under observation for 14d. In the sub-chronic study, 24 male and female BALB/c mice were divided into four groups and treated daily with test substance preparation at dose levels of 0, 50, 250, and 1250mg/kg body weight for at least 90 consecutive days. The mortality, body weight changes, clinical signs, hematological and biochemical parameters, gross findings, histopathological, and organs weight determinants were monitored during this study. Results: The results of acute toxicity indicated that the LD50 of alpha-L-guluronic acid is 4.8g/kg. We found no mortality or abnormality in clinical signs, body weight, relative organs weight, or necropsy in any of the animals in the subchronic study. Additionally, the results showed no significant difference in hematological, biochemical, and histopathological parameters in rats. Conclusions: Our results suggest that alpha-L-guluronic acid has high safety when administered orally in animals.