This study was established that after 3 months storage, olive mill waste (OMW) was enriched with hydroxytyrosol (HT) (2,652 mg/L) and contained only phenolic monomers. It also showed that HT supplementation to surviving diabetic rats decreases considerably intestinal maltase, lactase, sucrose, and lipase activities by 49, 31, 42, and 40%, respectively. In addition, HT enhanced the superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities by 330, 170, and 301%, respectively and reduced gluthation (GSH) level by 79% in pancreas compared to diabetic rats. Moreover, a significant decrease in the thiobarbituric acid reactive substances (TBARs) level and lactate dehydrogenase (LDH) activity in diabetic rats pancreas by 34 and 49% respectively after administration of HT. In addition, HT improved plasma triglyceride and cholesterol levels in diabetic rats by lowering low density lipoprotein (LDL)-cholesterol and triglycerides (TG) by 27 and 53%, respectively and increasing high density lipoprotein (HDL)-cholesterol content by 72%. These properties of HT are interesting regarding its use as therapeutic agent in biotechnological applications, especially in developing anti-diabetic and hypocholesterolemic drugs.