Anemia is defined as a decreased capacity of the blood to carry oxygen and is recognized by packed cell volume, erythrocyte, and hemoglobin values below reference ranges. Causes of anemia in birds include blood loss, heavy metal toxicosis, parasitic infection, and chronic disease. Several differences exist between avian and mammalian physiology, including the avian ability to tolerate greater losses of blood. However, the use of blood products has become an effective tool for treating anemic avian patients. Whole blood transfusions (autologous, homologous, and heterologous) and administration of hemoglobin-based, oxygen-carrying solutions are the treatments used most commonly in birds.