**1. Introduction**

According to World Health Organization (WHO), anemia is defined as a Hb level < 13 m/dl in adult males and postmenopausal females, while it is there if Hb levels <12 gm/dl for premenopausal females [1]. Renal anemia is a frequent complication in chronic kidney disease (CKD) patients with worse outcomes of morbidity and mortality [2, 3]. Its severity increases with progressive loss of kidney function, as around 90% of erythropoietin (EPO) is produced by the kidneys [4]. While almost 5% of CKD stage III patients have anemia, approximately 95% of hemodialysis patients develop a certain degree of anemia [5]. Several causative factors are included in the pathogenesis of anemia in CKD patients, mainly the decreased production of EPO [6]. Following the US Food and Drug Administration's approval of recombinant human EPO (rhuEPO) in 1989, the introduction of ESAs was a real revolution in renal anemia management [7]. More than 85% of hemodialysis patients were treated with ESA, according to USRDS 2020 Annual Data report. However, inadequate response to ESA therapy was reported in 5–10% of cases [8].
