Erythropoietin (EPO) antibodies are immune molecules that specifically recognize and bind to erythropoietin, a glycoprotein hormone essential for red blood cell production. Naturally produced by the kidneys, EPO stimulates erythroid progenitor cells in bone marrow. The development of EPO antibodies is primarily studied in two contexts: autoimmune disorders and therapeutic interventions. In rare cases, autoantibodies against endogenous EPO cause pure red cell aplasia (PRCA), a severe anemia characterized by ineffective erythropoiesis. More commonly, antibodies emerge as a complication of treatment with recombinant EPO (e.g., epoetin), particularly when administered subcutaneously or formulated with stabilizers that may enhance immunogenicity. These neutralizing antibodies can cross-react with both endogenous and exogenous EPO, leading to antibody-mediated PRCA. Structurally, EPO antibodies typically target epitopes in the protein's carboxy-terminal region or receptor-binding domain. Their detection employs immunoassays like ELISA or functional cell-based neutralization tests. Research on EPO antibodies has driven improvements in biopharmaceutical design and clinical monitoring protocols, while also providing insights into EPO's physiological interactions. Current therapeutic strategies focus on minimizing immunogenicity through modified EPO analogs and optimized administration routes.