${eta}$-Glucan purified from oats (OG) and bitter melon, Momordica charantia Linn (MC), water extracts have shown favorable effects on diabetes and its complications. We investigated to find out the optimal composition showing hypoglycemic and antidiabetic complication effects in variable compositions (OG:MC = 1:1, 1:2, 1:4, 1:6, 1:8, 1:10, 2:1, 4:1, 6:1, 8:1, 10:1). Extracts were administered orally once a day for 28 days following 7 days post streptozotocin (STZ) dosing. Five rats per group (total 15 groups; Intact, STZ, OG, MC, and the variable composition groups) were selected according to the blood glucose and body weight at 6 days after STZ dosing. After 28 days of extracts dosing, the changes on the body weight, liver and kidney weight, blood glucose, blood urea nitrogen (BUN), creatinine, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), low-density lipoprotein (LDL), and total-cholesterol levels were observed. As the result of STZ-induced diabetes, decreases of body weight, increases of the liver and kidney weights, blood glucose, BUN, creatinine, AST, ALT, LDL, and total-cholesterol levels in STZ control were detected compared with intact control. However, these changes of hyperglycemia, diabetic nephropathy, hepatopathy, and hyperlipemia were dramatically decreased in the OG and MC single-dosing group, and all composition groups. In addition, there were more favorable effects in all composition groups compared with the OG and MC single-dosing groups. Among variable compositions, the OG:MC 1:2 mixed group showed the most synergic effects in this study.