Because of increasing safety concerns related to erythropoiesisstimulating agents (ESAs), the Centers for Medicare & Medicaid Services issued a Medicare reimbursement policy change regarding these medications in cancer patients. However, the policy established an absolute hemoglobin or hematocrit threshold to qualify for reasonable use but did not take the effect of gender and racial/ethnic differences in hemoglobin levels into consideration. To examine disparities in the use of ESAs and blood transfusions after the Medicare policy change. This study was an exploratory treatment effectiveness study and used the SEER-Medicare linked database. The treatment group was composed of cancer patients, whereas the control group was composed of chronic kidney disease patients. An interrupted time series design was used to examine the effect of the Medicare policy change on the use of ESAs and blood transfusions in different gender and racial/ethnic groups. The Medicare reimbursement policy change had an immediate effect on reducing the use of ESAs by 50% and increasing the use of blood transfusions by 10%. The immediate effect of the policy change on the monthly utilization of ESAs was 2 times greater in females (60% reduction) than males (30% reduction). Females had a 10% immediate increase in the monthly utilization of blood transfusions after the policy change. The policy change had the same immediate effect of a 50% reduction on the use of ESAs for Whites, African Americans/Blacks, and Latinos. African Americans/Blacks had a 50% immediate increase in the monthly utilization of blood transfusions after the policy change. Gender and racial/ethnic disparities were associated with the Medicare reimbursement policy change in the use of ESAs and blood transfusions. Thus, future policy considerations should keep biologic differences across gender and racial/ethnic groups in mind. This study was funded by the SPARC Research Grant. The funder had no role in any part of this study. The authors have nothing to disclose.