Abstract: An active substance is extracted from an herbal composition which comprises: Centaurii umbellatum, Gentianaceae (centaury plant), Teraxacum officinale, Asteraceae (dandelion root), Juniperi communis L, Cupresaceae (juniper berry), Urticae dioica L, Urticeae (nettle plant), Urticae dioica L, Urticaceae (nettle root), Cichorium intybus L, Cichoriaceae (chicory root), Morus nigra L, Moraceae, (mulberry leaf), Achilleae millefolium L, Asteraceae (yarrow flower), Vaccinium myrtillus L, Ericaceae (bilberry leaf), Phaseolus vulgaris L, Fabaceae (bean pods), Valeriana officinalis L, Valerlanaceae (Valerian root). The active substance is used in the manufacture of pharmaceutical compositions used in connection with control of diabetes mellitus type II.