The purpose of this study is to evaluate the effect of Ribes khorassanicum hydro ethanolic extract supplementation on metabolic parameters of type 2 diabetic patients. The study design is randomized, double blind (both patients and researchers) placebo controlled trial. The study population consists of type 2 diabetes patients (aged 35–60 years) presenting to Diabetes clinic (Emam Reza Hospital, Mashhad University of Medical Sciences). One hundred eligible patients will be chosen and assigned to intervention and placebo groups by random allocation (Permuted block randomization). Patients with 6 months diagnosed diabetes and treated with anti-diabetic drug will be included. Patients with cardiac, renal, hepatic diseases and who had concomitant infections, insulin injection, smoking, pregnancy and breastfeeding, recent (in the last month) and concurrent use of herbal medications, aspirin and anticoagulant drug will be excluded. The patients will be treated with Ribes khorassanicum hydro ethanolic extract (1 capsule=500 mg, every 12 h) or placebo for 3 months. Before and at the end of the study, patients' blood samples will be taken and fasting blood sugar, 2-h post-prandial, glycated hemoglobin, fasting insulin, fasting blood levels of lipids, liver enzymes and creatinine will be measured. Body mass index, diastolic and systolic pressure will be evaluated too.