The invention relates to the field of biotechnology and medicine, and specifically to insulin-containing injectable formulations used, in particular, for treating diabetes mellitus. The present formulation comprises insulin and a pharmacologically acceptable polymer having a hydrodynamic diameter of more than 4.5+/-0.5 nanometers. As said polymer, at least one polymer having a molecular weight of 20-70 kDa may be optimally used, and is selected from a group including: dextran, polyethylene glycol and albumin. As regards insulin formulations used, it is possible to use human recombinant insulin and genetically engineered analogs thereof used in the commercial formulations. Experiments have shown that using the aforementioned polymers provides insulin formulations with a prolonged effect without the use of chemical or genetic methods of modifying insulin molecules. The method of long acting formulations preparing is not dependent on biotherapeutics and thus it can be used over range of therapeutic proteins.
