The blood is made of three types of cells - erythrocytes (red blood cells), leukocytes (white blood cells) and platelets. Red blood cells are disc-shaped, and are continually produced in the bone marrow. This is because they only live for about 120 days. Red blood cells contain hemoglobin, which is a red, iron-rich protein that carries oxygen from the lungs to the body's muscles and organs. These cells also remove carbon dioxide (a waste product) from cells and carry it to the lungs to be exhaled.
White blood cells are part of the body's immune system, and they fight off disease and infection.
Platelets help blood clot and live an average of six days.
Anemia occurs when the body does not have enough red blood cells. Individuals who are anemic may experience fatigue because the heart has to work harder to deliver oxygen to the muscles and organs. There are many possible causes of anemia, including chronic diseases, bone marrow disorders, iron deficiency, vitamin deficiencies and genetic abnormalities (like sickle cell anemia).
Anemia is a common blood disorder, affecting an estimated 3.4 million people in the United States. Women and individuals with chronic diseases are at an increased risk for anemia. Many forms of anemia are mild, short-term and can be easily treated. However, other forms can be long-term and more severe.

Related Terms

Anemic, aplastic anemia, blood, blood disorder, erythrocytes, fatigue, ferritin test, folate, folic acid, hemoglobin, hemoglobin electrophoresis, hemoglobin S, hematocrit, iron deficiency, leukocytes, megaloblastic anemia, microcytic anemia, pernicious anemia, platelets, red blood cells, sickle cell disease, TIBC, total iron-binding capacity, vitamin deficiency anemia, vitamin B-6, vitamin B-12, white blood cells.