According to the National Heart Lung and Blood Institute (NHLBI), severe or long-term anemia is potentially fatal. Oxygen is not properly delivered by the blood within a body under this condition and this sometimes leads to damage of the heart, brain or other vital organs.
The NHLBI explains that anemia is caused by an insufficient number of red blood cells or a limited supply of the protein "hemoglobin." Red blood cells transport oxygen throughout the body, and hemoglobin is necessary to carry out that function. Several conditions lead to anemia, including excessive blood loss, poor diet, pregnancy and diseases that interfere with red blood cells. Treatment options include dietary changes, vitamin and mineral supplements, surgery and blood transfusions.