The invention relates to a composition in the form of an injectable aqueous solution, the pH of which is between 6.0 and 8.0, comprising at least: a) a basal insulin, the isoelectric point pI of which is between 5.8 and 8.5 b) a co-polyamino acid bearing carboxylate charges and substituted with hydrophobic radicals. In one embodiment, the compositions according to the invention also comprise a prandial insulin and/or gut hormone.