Abstract: The effects of MSH on whole blood viscosity (WBV)and hematocrit (Ht) levels in short-term alloxan-induced diabetic were studied. Male and Female Sprague-Dawley diabetic rats weighing 185-250 g were given intraperitonially (i.p.) a daily injection of 20 mg alloxan solution/100 g of body weight for 10 days. Normal and diabetic rats were given daily injection (i.p.) of alpha-Melanocyte stimulating hormone (MSH) at a dose of 2 μg/100 g b.w for 10 days. Body weight, serum glucose, serum insulin, Ht and WBV were measured. The results indicated that MSH decreased serum glucose levels in diabetic rats in comparison with normal rats. Our study demonstrates that MSH administration significantly lowers blood viscosity of short-term diabetic rats. It proposed that MSH may exert a protective effect on the vascular endothelial cells.