There are more than 100 types of anemia. Some of the most common include:

• Iron deficiency anemia. This form of anemia is by far the most common. Iron is necessary for the bone marrow to produce hemoglobin. Without this essential mineral, the body fails to produce enough hemoglobin for red blood cells. In addition to food, the usual way for the body to obtain iron is to recycle the iron from blood cells that have died and use it to create new blood cells. Thus, when blood is lost, so is the iron. This process explains why an iron-poor diet, heavy menstrual periods or a growing fetus in a pregnant woman can cause iron deficiency anemia. In men, iron deficiency anemia means that bleeding has occurred somewhere in his body.
  
  
• Sickle cell anemia. More than 70,000 Americans have sickle cell anemia, making it the most common inherited blood disorder in the United States, according to the National Institutes of Health (NIH). This condition disproportionately affects African Americans at a rate of one out of every 500. Sickle cell anemia is an inherited disease marked by a chronic shortage of red blood cells due to a defective form of hemoglobin.
  
  
• Vitamin deficiency anemia. In order to produce red blood cells, the body requires vitamin B12, folic acid and other key nutrients. A diet that is lacking in these essential nutrients can lead to decreased production of red blood cells. Intestinal disorders that reduce the amount of nutrients the body can absorb are a common cause of this type of anemia. The category for all vitamin deficiency anemias is megaloblastic anemias. With this group, the bone marrow of affected individuals produces large, irregular red blood cells (megaloblasts). Examples of vitamin deficiency anemia include megaloblastic anemia and pernicious anemia.
  
  
• Hemolytic anemias. This group of anemias develops when red blood cells are abnormally destroyed within the body. Autoimmune diseases and certain blood disorders can cause hemolytic anemias. Some medications, including antibiotics, can also break down red blood cells causing this condition.
  
  
• Anemias associated with bone marrow disease. The production of blood in the bone marrow can be affected by a variety of diseases, including leukemia, myelodysplasia (MDS, a pre-leukemia condition), multiple myeloma, myeloproliferative disorders, lymphoma and metastatic cancer. The severity of these types of anemias can range from a mild alteration to a potentially fatal shutdown in the production of blood.
  
  
• Aplastic anemia. This rare form of anemia occurs in one to two people for every million residents of the United States, according to the American Cancer Society (ACS). It is seen more often in developing countries where there is greater exposure to toxic chemicals. In this form of anemia, the bone marrow does not make blood cells. While aplastic anemia can be a sign of certain cancers that affect bone marrow (such as leukemia), it is not a type of cancer itself. Exposure to chemicals, such as benzene, as well as chemotherapy drugs and radiation treatment, can cause this type of anemia. It can also be a primary immune disease.
  
  
• Idiopathic anemia. Despite their best efforts, physicians are sometimes unable to determine the cause of anemia in a patient. These cases are labeled idiopathic anemias. These patients should be followed at regular intervals for delayed manifestations of a cancer or other cause of anemia.

There are many other types of anemia which affect a smaller number of people and have an abnormal form of hemoglobin. Thalassemia is one example of an inherited blood disorder that causes mild to severe anemia. This blood disorder is found among individuals of Mediterranean descent, such as Italians and Greeks. These hereditary anemias are called hemoglobinopathics.