There is an increasing interest against to fight of diabetes by using hypoglycemic plants in the world. The public thinks that Heracleum persicum (HP) has antidiabetic effect local consumer in Turkey. As far as our literature survey, no studies have been reported so far on antidiabetic effects and toxic risk potential of the HP lyophilized extract supplementation used in this study. The aim of this study, for the first time, was to investigate the therapeutic effects of diabetic complications, antioxidant properties and toxic risk potential of HP against experimentaly streptozotocin (STZ) induced diabetes in rats, which were evaluated by measuring the level of serum biomarker released diabetes complications changes such glucose, insulin, c-peptide, lipid profile (LP), hepatic and renal damage biomarkers (HRDB), glucosylated hemoglobin (HbA1c), antioxidant defense system constituents (ADSCs), malondialdehyde (MDA) content measured in erythrocyte, brain, kidney and liver tissues, and alpha-glucosidase activitiy of small intestine. The plant aqueous extract was allowed to freeze-dried under a vacuum at - 54 degrees C to obtain a fine lyophilized extract. The study was performed on STZ-induced diabetic rats (45 mg/kg, body weight (bw), intraperitonally) designed as normal control (NC), diabetic control (DC), diabetes + acarbose (DAC) (20 mg/kg, bw), diabetes + HP (100 mg/kg, bw) (DH1), diabetes + HP (200 mg/kg, bw) (DH2) and diabetes + HP (400 mg/kg, bw) (DH3)] groups. The experimental process lasted 21 days.