EPO and cancer: It binds to specific receptors on the cell surface of RBC precursors in the bone marrow, stimulating the formation of enucleated reticulocytes, which rapidly mature into RBCs, causing an increase in the circulating red blood cell mass.29 Normally, a decrease in the haemoglobin level is accompanied by an increase in the serum EPO level, which will ultimately normalize the haemoglobin level.30 The relationship between haemoglobin and EPO is less apparent in patients with chronic diseases, such as cancer and chronic viral infections.