Anemia is an inadequate supply of red blood cells, resulting in a decrease in the oxygen-carrying capacity of the blood. A common reason that cancer patients experience anemia is as a side effect of chemotherapy. Anemia is important because it may cause unwanted symptoms, such as fatigue, tiredness or shortness of breath, and may exacerbate or cause other medical problems, such as a heart condition. Fortunately, anemia can be effectively managed.