EPO is a glycoprotein that is glycosylated up to 40-60 % , which causes its molecular weight to vary from 30-34 kD depending on the carbohydrate percentage. Hypoxia induces erythropoiesis, and hypoxia inducible factor (HIF) is directly involved in EPO expression. HIF-Prolyl hydroxylase (HIF-PH) is a sensor of levels of iron, oxygen, and metabolic activity. High levels of HIF protein induces EPO production in the kidneys and liver, and mobilizes iron to support erythropoiesis. EPO has been used in the treatment of anemia associated with chronic kidney disease, treatment of cancer patients on chemotherapy, and antiviral HIV therapy.