The present study aimed to assess the therapeutic effect of the unfermented and fermented cow; oat milk (CM, OM, FCM, and FOM) and fermented oat milk supplemented with 2% whey protein concentrate (FOM+WP) in diabetic rats. Alloxan was applied for inducing diabetes and hyperlipidemia in rats. The rats were randomly divided into two main groups. Control (-) (6 rats) were fed on a standard diet, while the second group (42 diabetics rats) were divided into six groups (6 rats each), and treated by different unfermented and fermented milk types by epigastric tube for 4 weeks. After four weeks, all treatments reduced the level of glucose, the serum levels of TC, TG and LDL-c compared to control (+) group and this was associated with a significant increase (p<0.05) in HDL-c in these groups. The highest significantly (p<0.05) decrease recorded in the groups fed with (OM) and (FCM), respectively. Liver enzymes activity decreased significantly (P˂0.05) in FOM + WP, FOM, FCM and OM groups, respectively. Feeding the rats on fermented oat milk fortified with whey protein led to decrease the fecal total anaerobes and fecal enterobacterial counts and stimulate the viability of both fecal lactobacilli and bifidobacteria in the intestinal colon, compared with other treatments. Histopathological examination of the liver sections showed no histopathological alteration in the hepatic parenchyma in (FOM+WP) group. (OM) and (FCM) groups showed no histopathological alteration and the islands of Langerhans cells were in normal size as well as the surrounding acini and ducts. In conclusion, treatment with oat milk led to curing hyperglycemia and hyperlipidemia in diabetic rats. Meanwhile, treatment with fermented oat milk fortified with whey proteins resulted in a better effect on the liver and improved the growth of the health-promoting intestinal microflora.