What Causes Anemia?

There are three main causes of anemia: blood loss, lower than normal levels of red blood cell (RBC) production, or higher than normal rates of RBC destruction. More than one of these factors can combine to cause anemia.

Blood Loss

Blood loss is the most common cause of anemia, particularly iron-deficiency anemia. Blood loss can be short term or persist over time. It can be caused by heavy menstrual periods, bleeding in the digestive or urinary tracts, surgery, trauma, or cancer. If bleeding is significant, the body can lose enough RBCs to cause anemia.

Low Levels of RBC Production

Lower than normal levels of RBC production can result from a poor diet that lacks iron, folic acid, or vitamin B12. It also can be caused by conditions that make it difficult for the body to absorb nutrients into the blood.

Chronic diseases like kidney disease and cancer can decrease the body’s ability to produce enough RBCs. Infections, medicines, or radiation used to treat another disease or condition may damage the bone marrow, making it unable to produce RBCs fast enough to replace those that die or are destroyed.

During pregnancy, the fetus needs additional blood cells to develop. The mother may not be able to produce enough RBCs for herself and the fetus, which can result in anemia.

High Rates of RBC Destruction

Higher than normal rates of RBC destruction can be the result of inherited blood disorders like sickle cell anemia, thalassemia, and certain enzyme deficiencies. These disorders create abnormalities in the RBCs that cause them to die off in a shorter period of time than healthy RBCs. In people with hemolytic anemia, the immune system mistakenly attacks RBCs. This destroys the RBCs faster than the body can replace them.