Respiratory system and Cardiovascular system.
Anemia is, by definition, low red blood cells or low hemoglobin. When anemia develops for a long period of time, our heart will have to increase its output, which means, it has to work harder to pump the blood and oxygen that it has, throughout the body. Meanwhile, the lungs are also compensating for the lack of oxygen and the excess of carbon dioxide coming from the cells, by increasing breathing rate.