The invention relates to a composition in aqueous solution, including insulin and at least one substituted anionic compound chosen from substituted anionic compounds consisting of a backbone formed from a discrete number u of between 1 and 8 (1≦u≦8) of identical or different saccharide units, linked via identical or different glycoside bonds, said saccharide units being chosen from the group consisting of hexoses, in cyclic form or in open reduced form, said compound comprising partially substituted carboxyl functional groups, the unsubstituted carboxyl functional groups being salifiable. The invention also relates to a pharmaceutical formulation comprising a composition as claimed in any one of the preceding claims.
