High blood glucose levels of KK-A(y) mice with type 2 diabetes mellitus were normalized by daily intraperitoneal (ip) administration of a zinc(II) complex, bis (maltolato)zinc(II) (Zn(Mal)(2)) with a Zn(O-4) coordination mode, following the finding of strong in vitro insulinomimetic activity in isolated rat adipocytes treated with epinephrine in terms of the inhibition of free fatty acid release. The blood glucose level was maintained in the normal range during administration of the Zn(Mal), complex for 14 days and improvements in the glucose tolerance were confirmed by an oral glucose tolerance test.