Quick-acting insulin formulation including a substituted anionic compound

The invention relates to a composition in an aqueous solution, including insulin and at least one substituted anionic compound selected among the substituted anionic compounds consisting of a backbone made of a discrete number u comprised between 1 and 8 (1 ≤ u ≤ 8) of identical or different saccharide units, bonded by identical or different glycosidic bonds, said saccharide units being selected from the group comprising hexoses, in cyclic form or in open reduced form, said compound comprising partially substituted carboxyl functional groups, the non-substituted carboxyl functional groups being salifiable. The invention also relates to a pharmaceutical formulation including a composition according to any one of the preceding claims.