Introduction: Chronic inflammation plays an important role in the development and progression of diabetes and diabetic nephropathy as one of its major complications. Vitamin D3 regulates two separate, but interacting, types of immunity: innate and adaptive. Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are markers of inflammation.The aim of the study was to determine the values of NLR and PLR in patients with diabetic nephropathy and vitamin D3 deficiency, before and after correction of vitamin D3 levels. Materials and Methods: Participants with diabetes type 2 and diabetic nephropathy were divided into two groups: study and control group of 45 patients each, with vitamin D3 deficiency and comparable characteristics in terms of therapy and laboratory parameters. The study group of patients received cholecalciferol at a dose necessary to achieve the intended optimal vitamin D3 level of 90-100 nmol /L in the blood, while the control group received their previous therapy. Results: The NLR in the study and control groups together on inclusion was 2.36 ? .98 and for PLR 121.77 ? 42.24. NLR was lower in women (2.18 ? .72) than in men (2.58 ? 1.01) as well as PLR was lower in women (118,59?57,51) than in men (123,15?54,43). A continuous positive effect on NLR, which has statistical significance, was found in group ( p = 0.047; and p = 0.011), as well as in men (p= 0.001; and p = 0.006). Conclusion: Vitamin D3 correction exerts anti-inflammatory activity in patients with diabetic nephropathy that is most pronounced on neutrophil-to-lymphocyte ratio and less on platelet-to-lymphocyte ratio.