Increased haemopoiesis due to erythropoietin in some patients may cause overproduction of cytokines (interferons that suppresse haemopoiesis) which give rise to flu like symptoms which is also a complication of therapeutic cytokines.

It is also important to compare levels of interferon alfa and IL-6 in those patients with flu like symptoms and those without but are all on erythropoietin therapy.

The other cause may be hypersensitivity reaction due to albumin which is part of the erythropoietin formulation.