EPO and vitamin D deficiency: A randomized control trial conducted by Rianthavorn et al. has shown that vitamin D insufficiency leads to erythropoietin resistance in CKD and administration of vitamin D decreases the need for erythropoietin [8]. Another study found that vitamin D use in vitamin-D-deficient patients lessens the need for erythropoietin [9]. However, a meta-analysis conducted to see the relationship between vitamin D supplementation and hemoglobin concentration found no significant association between them [10].