The state of cellular homeostasis in diabetic patients was assessed by the permeability of erythrocyte membranes, which can serve as an indicator of functional disorders of the vascular wall. It was found that the value of cytoplasmic membrane permeability depends largely on the variations in the ratio of cholesterol and phospholipids. An absolute or relative increase in membrane cholesterol content is accompanied by stabilization of cellular structures, which, in turn, leads to a decrease in permeability to non-electrolytes and ions and changes in the activity of membrane-bound enzymes.