AIM: The aim of this study was to examine the effects of vitamin D supplementation in patients newly diagnosed with type 1 diabetes (T1D) assessed by insulin needs and changes in glycemic indices, as evidenced by randomized controlled trials (RCTs). METHODS: A total of 7 RCTs were retrieved from PubMed/Medline and EBSCO databases by MeSH term search, and were reviewed systematically. The RCTs included examined the effects of alphacalcidole (n = 2), cholecalciferol (n = 2), and calcitriol (n = 3) supplementation on changes in daily insulin dose (DID), fasting Cpeptide (FCP), stimulated C-peptide (SCP), and HbA1c. In total, 287 individuals, diagnosed with T1D within a period of 4 weeks to 1 year and aged between 5 to 38 years, were examined. RESULTS: Significant positive effects on DID, FCP, and SCP levels were observed after supplementation with alphacalcidole and cholecalciferol, whereas supplementation with calcitriol showed no effect. CONCLUSIONS: Vitamin D supplementation in the form of alphacalcidole and cholecalciferol appears to be beneficial in the treatment of T1D patients by attenuating the natural history of the disease.