We aimed to investigate median lethal dose (LD50) and hypoglycemic effect of fixed oil of Foeniculum vulgare Miller seed fixed oil (FFO) in mice and its hepatoprotective effect on carbon tetrachloride (CCl4) induced liver injury model in rats. Method: Extract of FFO, glibenclamide (as a reference group) and physiologic saline (control group) were administrated to the healthy and diabet occured mice with alloxan. Before treatment in the first, second, third, fourth and 24th hours, blood was taken from the vena coccygea of mice. Blood glucose levels were measured. Twenty-four Sprague-Dawley rats were divided into four groups (n=6), and the groups treated daily for seven days, by i.p. injections, of isotonic saline solution (ISS), olive oil, carbon tetrachloride (CCl4), CCl4 + FFO respectively. Results: FFO did not significantly reduced blood glucose in alloxane-induced diabetic mice compared to ISS control group. In contrast, glibenclamide effectively reduced blood glucose of alloxane-induced mice in first, second, fourth and 24th hours as expected. In the CCl4-treated group and FFO-treated group serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) levels were quite high. In contrast, the control groups (group I and group II) had significantly lower levels of AST and ALT when compared with the CCl4 and FFO groups. Conclusion: The results of this study indicate that FFO has neither a potent hepatoprotective effect against CCl4-induced hepatic damage in rats nor a hypoglycemic action in mice. The LD50 of FFO was determined as 5.52 mL/kg.Keywords: Foeniculum vulgare Miller, fennel fixed oil, median lethal dose, hepatoprotective effect, hypoglycemic effect.