Brief Summary:

Study content: This is a multicentre, double-blind, randomised controlled study to determine the optimal dose and duration of treatment for the correction of vitamin D insufficiency or deficiency in patients with CKD5d; to investigate whether vitamin D supplementation delays the increase in PTH levels in this group of patients; and to investigate the effects on changes in CKD-MBD-related markers, cardiovascular complications, cognitive function in this group of patients. 2. Study procedure: Based on the inclusion and exclusion of the patients, the study was conducted in accordance with the following criteria Study procedure: Eligible subjects were screened according to inclusion and exclusion criteria and randomly divided into three groups: high-dose vitamin D group, low-dose vitamin D group and control group. Baseline data were collected before the intervention and each group was given different doses of regular vitamin D2 softgels or placebo and followed up. 25(OH)D, PTH, blood Ca, and blood P levels were measured every month; bone metabolism markers, FGF23, and blood counts, liver function, kidney function, lipids, and blood glucose were measured every 3 months; the prevalence of vascular calcification, the incidence of cardiovascular events, and changes in cognitive function scale scores were assessed 6 months after the intervention.