Background & Aim:Ocimum gratissimumis an aromatic plants used among traditional medicine practitioners in the treatment of warts, diarrhoea, headache, diabetes etc. This study aimed at evaluating the anti-diabetic and toxicity profile of aqueous leaf extract of the plant in alloxan-induced diabetic rats.Experimental: Thirty albino rats (111.33 ±1.50g) were grouped into six (A-F) groups of animals. Group A received 0.5 ml distilled water (p.o) for eight days. Diabetes was induced in group B-F animals using 160 mg/kg alloxan (i.p ) and thereafter administered 2.5 metformin, 125, 250 and 500 mg/kg aqueous leaves extract of Ocimum gratissimum, respectively (p.o) for 8 consecutive days. Blood sugar level was taken 1 h after drug administration every other day. Body weights of animals were taken before induction, after induction, and on the 8th day. Blood samples and organs (liver, kidney, and pancreas) were collected for biochemical assays and histopathological examinations.Results: Alloxan significantly (p <0.05) increased the glucose, albumin, urea, creatinine, bilirubin, Alkaline phosphatase (ALP), Aspartate transaminase (AST) and Alanine transaminase (ALT) levels of rats compared with the distilled water group. The aqueous leaves extract of Ocimum gratissimum significantly (p <0.05) reduced the glucose, albumin, urea, creatinine, bilirubin, ALP, AST and ALT levels compared with the diabetic untreated rats. There were no significant histological changes in the liver, pancreas and kidneys of diabetic treated rats compared with diabetic untreated rats which exhibited moderately distorted organ degeneration.Recommended applications/industries: Aqueous leaves extract of Ocimum gratissimum possesses anti-hyperglycemic effects and is relatively safe for use in the treatment of diabetics. Manuscript profile