Anemia describes one of a number of diseases that leads to a shortage of red blood cells in the blood. It has a number of causes, which fall into four general categories:
- Shortage of material to create new blood cells (e.g. iron deficiency).
- A malfunction of the bone marrow that creates red blood cells, such as is common with several forms of cancer (e.g. aplastic anemia).
- The destruction of red blood cells by a foreign material.
If untreated, anemia is invariably fatal. Many forms of anemia can be treated by treating or managing the underlying condition. However, when red blood cell counts fall below a certain level, a blood transfusion is usually required to replenish the level of red blood cells in a patient.