Vitamin D status and the relationship between serum 25(OH) vitamin D concentrations and the components of insulin resistance were examined in 120 patients with chronic kidney disease stage 2 and 3. Insulin sensitivity/resistance was calculated by the quantitative insulin sensitivity check index (QUICKI). In this analysis, the prevalence of insulin resistance was 42 %. Only 17 % of patients had serum 25(OH) vitamin D concentration in the recommended range ( ≥ 30 ng/ml), 42 % suffered from vitamin D insufficiency and 41 % had moderate vitamin D deficiency. Insulin resistance significantly correlated with serum 25(OH)D and 1,25(OH) 2 D concentrations, renal function and protein excretion rate. Our results support the increasing evidence that vitamin D deficiency may be one of the factors participating in the development of insulin resistance already in the early stages of chronic kidney disease. and K. Štefíková ... [et al.].