The relevance of the study of glycemic variability in patients with diabetes mellitus and diabetic nephropathy is due to disability of the able-bodied population and high mortality against the background of the almost irreversible progression of diabetic nephropathy. The article highlights modern ideas about the influence of various factors on the occurrence of diabetic nephropathy and its course. The article is devoted to a review of current recommendations on diabetes mellitus and diabetic nephropathy; the etiopathogenesis of diabetic nephropathy was described in detail. The role of the kidneys in glucose homeostasis, renal gluconeogenesis, and glucose reabsorption by the kidneys in healthy and in pathology is described. Detailed expositions of glycemic variability parameters, their changes in patients with diabetes mellitus depending on the stage of diabetic kidney damage are presented. The role of the kidneys in maintaining energy homeostasis, impaired glucose homeostasis in conditions of chronic kidney disease is described. We analyzed different options for insulin therapy, their advantages, and disadvantages in patients with diabetes mellitus with diabetic nephropathy. The presented material is extremely relevant for the development and implementation in the clinical practice of glycemic control methods to optimize treatment tactics, prevent the formation of microvascular complications, and early disability of patients with diabetes mellitus.