Anemia is a disorder in which the blood has less hemoglobin or fewer red cells than normal. With less hemoglobin, the blood carries less oxygen to the body's cells, which causes weakness, fatigue, and paleness in the anemic person. If hemoglobin levels drop low enough, the patient could die. Anemia can be caused by a diet deficient in iron or by heavy bleeding; these anemias are relatively simple to treat with supplemental iron and iron-rich foods. Anemia can also result from a failure of red cells to develop normally, from excessive destruction of red cells in the blood, and from a failure of the bone marrow to produce red cells. These anemias are more difficult to treat.

The first recognized anemia was chlorosis, or "the green sickness," common in girls until the early 1900s. Although the condition was recognized as early as the 1500s, the sickness itself was...