The goal of this observational study is to learn about the effects of cholecalciferol administration, according to guidelines for the general population, on laboratory parameters of Chronic Kidney Disease-Mineral and Bone Disorder in dialysis patients, depending of the attained levels of vitamin D (25OH)D). The main question it aims to answer is: How does cholecalciferol affect calcium and phosphate metabolism parameters depending on the achieved levels of 25(OH)D? Participants taking cholecalciferol as part of their regular medical care for CKD-MBD will have the laboratory result parameters observed for up to 4 years.