The invention relates to a complex between an insulin and a polysaccharide comprising carboxyl functional groups, said polysaccharide being chosen from polysaccharides functionalized with at least one phenylalanine derivative, noted Phe, said phenylalanine derivative being chosen from the group consisting of phenylalanine and its alkali metal cation salts, phenylalaninol, phenylalaninamide and ethylbenzylamine or from phenylalanine esters, and said insulin being either a human insulin or an insulin analog. The invention also relates to a pharmaceutical composition comprising at least one complex according to the invention, especially in the form of an injectable solution.