This book is about the evaluation of the hypoglycemic and protective effects of mixture of five selective medicinal plants: Trigonella faenum-graecum seeds, Nigella sativa seeds, Zingiber officinale rhizomes, Olea europeae leaves and Fraxinus ssp. seeds, and determine the efficacy of this mixture in the treatment of diabetes mellitus type 2. The hyperglycemia was induced by alloxan in male rats model. This study has involved many phytochemical tests such as characterization of 20% methanolic extract of each plants which has been carried out by thin layer chromatography, detection phytochemical compounds and antioxidant activity test. Furthermore, cytogenetic and molecular study was carried out which included determination of mitotic index, chromosome aberration, and DNA fragmentation test of DNA extracted from WBC and renal cortex. On the other hand, insulin receptor and insulin receptor substrate-1 genes had been detected in all treatment and control groups. Also, histopathological changes in pancreas, liver, and kidney were studied.