A composition in the form of an injectable aqueous solution, with pH from 3.5 to 4.4, including at least human insulin A21G and at least one glucagon suppressor with prandial action. In an embodiment, the glucagon suppressor with prandial action is selected from an amylin analog or an amylin receptor agonist or a GLP-1 analog or a GLP-1 receptor agonist (GLP-1 RA). In an embodiment, the glucagon suppressor with prandial action is an amylin analog or an amylin receptor agonist. In an embodiment, the glucagon suppressor peptide with prandial action is pramlintide. Also, a method for obtaining human insulin A21G, includes at least one step of reacting human insulin A21G, B31R, B32R (insulin glargine) with rat carboxypeptidase B at an insulin/carboxypeptidase ratio from 500 to 2000, at a pH from 7.5 to 8.5 and a temperature from 20 to 30° C. for 10 to 20 hours.
