Summary: During the last decades, it has become known that due to the widespread distribution of 1α-hydroxylase and the vitamin D receptor (VDR), the extra-renal organs possess the enzymatic capacity to convert 25(OH)D to 1,25(OH)2D. A growing body of evidence has supported the importance of vitamin D pleiotropic effects in many extra-skeletal tissues, exerted in an endo-, auto-, or paracrine manner. Many studies have shown that vitamin D deficiency is associated with the worsening of various conditions such as diabetes, hypertension, cardiovascular disease, autoimmune and neurodegenerative disorders, malignancies, and increased mortality. In light of these data, the high prevalence of vitamin D deficiency becomes a significant public health problem worldwide. It is of particular importance in patients with chronic kidney disease (CKD), among whom the deficiency’s prevalence has been reported to reach 80%. In the article, specific features of vitamin D metabolism in CKD have been shortly discussed, and the current recommendations for vitamin D status monitoring and its supplementation are presented.