A zinc(II) complex which is lowly toxic, has high insulin-like activity, and is effectively usable as a hypoglycemic agent for the prevention or treatment of diabetes; a hypoglycemic agent containing the complex; a medicinal preparation which contains the complex and is useful as a preventive/remedy for diabetes; and a food containing the complex, such as a health food or supplementary health food. The hypoglycemic agent contains an organic zinc(II) complex having as a ligand a compound selected among aminoalkylpyridines, bis-optically active amino acids, bisaminoalkylcarboxylic acids, oligopeptides, oligopseudopeptides, di-substituted aminocarboxylic acids, .alpha.- and .beta.-hydroxycarboxylic acids, vitamins, glutamine derivatives, etc.