Studies of membrane receptor system in patients with insulin-dependent diabetes mellitus revealed that insulin resistance in pregnant patients with type I diabetes is caused by disordered cellular sensitivity to threshold physiological and submaximal insulin doses, whereas the maximal doses of the hormone normalize glucose consumption by the cells. High insulin doses intensify lipid peroxidation, normalize the status of membranous proteins, reduce the number of thiol groups, reduce AOA level in membranes, and, hence, reduce membranous capacity to bind active peroxide radicals. Structural and functional changes in red cell membranes are associated with reduced affinity of insulin receptors, reduction in the number of insulin-binding sites in membranes, this disordering intracellular effects of insulin.