EPO and anemia (phenotype): From the 1950s to 1980s Co was used in the treatment of anemia due to its potential to stimulate erythropoietin production, and polycythemia was described resulting from ingestion of Co. Among the published literature, Co doses resulting in blood Co concentrations of approximately 300 μg/L or less have not been associated with hematological responses, while blood Co concentrations of approximately 600 μg/L and higher have consistently been associated with polycythemia and increased hemoglobin content (Finley et al. 2012).