The present study evaluated the acute toxicity effect of Lasianthera africana leaf extract on normal rats and effect of the extract on the hepatic and renal function indices in alloxan-induced diabetic rats. In the acute toxicity test, male Wister rats received orally four different single dose of the extract and were kept under observation for 14 days. The result indicates that LD 50 of the extract is higher than 5,000 mg/kg body weight. For the second experiment, doses (50, 100 and 200 mg/kg body weight) of the leaf extract were administered orally to alloxan-induced diabetic rats for 28 days and the effect of the treatment on blood glucose, hepatic enzymes, serum proteins and renal function indices was evaluated. The result indicates progressive and significant (p>0.05) reduction in fasting blood glucose. The extract also exhibited significant (p<0.05) reduction in serum aspartate aminotransferase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP), and significant (p<0.05) increase in serum total proteins and globulin and marginal (p>0.05) reduction in serum creatinine and uric acid relative to the diabetic control group. The results suggest that the leaf extract is safe and may be beneficial in the management of diabetic mellitus.