Anemia is a condition in which the oxygen-carrying capacity of the red blood cells is reduced. The red blood cells, or erythrocytes, contain molecules called hemoglobin that bind oxygen. Oxygen is picked up from the lungs on the hemoglobin molecules and transported through the blood throughout the body to tissues as required.
There are many causes of anemia. Anemia may result from deficiencies of substances needed to produce red blood cells: iron, vitamin B12 (cobalamin), or folate (folic acid). Those at risk have inadequate dietary intake or absorption of these substances or increased requirements. Iron deficiency is the most common cause of anemia. According to one national survey, 3% to 5% of females between 16 and 49 years of age and 3% of children between 1 and 2 years of age have anemia due to iron deficiency. Iron requirements increase during rapid periods of growth in young children and adolescence and during pregnancy. In addition, dietary iron ingestion may not be enough to counter blood loss in menstruating women. Strict vegetarians are at risk for developing iron and vitamin B12 deficiencies, whereas folate deficiency is more common among alcoholics and others with poor diets. Folate is destroyed by heat, putting those who eat primarily overcooked or canned foods at risk for deficiency. In addition to poor intake, some individuals may be unable to absorb iron, vitamin B or folate because of specific disorders (e.g., pernicious anemia, sprue) or prior gastrointestinal surgeries (e.g., gastrectomy). Some medications can impair the body’s ability to use folate properly. Blood loss or destruction of red blood cells within the body due to exposure to specific toxins (e.g., naphthalene in mothballs, fava beans) may also cause anemia. Anemia is also associated with chronic infections and diseases such as renal failure, cancer, and arthritis.
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There are many symptoms of anemia, but most are vague. Patients with anemia may complain of fatigue, coldness, weakness, dizziness, or sore tongues. Pale skin and fingernail beds may be noted. In more pronounced anemic states, the heart rate may be increased and chest pain or shortness of breath may be reported. Infants and young children with anemia are at risk for developmental delays and behavioral disturbances. In addition, patients with vitamin B12 or folate deficiency anemia may have neurological symptoms such as irritability, changes in memory, and tingling or numbness of the extremities.
The diagnosis of anemia is dependent on documentation of low hemoglobin and hematocrit levels in the blood. The normal values are higher in adult men than in adult women and also change from infancy through childhood. Other laboratory abnormalities depend on the cause of the anemia itself. For example, the mean corpuscular volume (MCV), the size of the red blood cell, will be low if the anemia is due to iron deficiency, but high if due to vitamin B12 or folate deficiency. A careful dietary and medical history should be accompanied by measurement of serum iron, vitamin B12, and folate concentrations to establish the cause of the anemia.
The treatment of the anemia is dictated by the cause. Patients with iron deficiency are commonly give a several-month course of ferrous sulfate or other iron salt until hemoglobin levels return to normal and iron stores are repleted. Vitamin B12 is available as oral tablets and may also be given as monthly intramuscular injections for those with medical conditions that affect absorption. Folate is generally given orally once daily. Patients with acute blood loss or dramatically low hemoglobin levels may also be given blood transfusions to correct the anemia immediately. Treatment of underlying causes (e.g., cancer, chronic infections) will also improve anemia. Patients with anemia due to kidney disease often receive injections of drugs that increase the production of red blood cells by the bone marrow. The development of anemia may be prevented by the use of folate, vitamin B12, and iron supplements in pregnant women and others at risk for deficiency.
- Centers for Disease Control and (1998). Recommendations to prevent and control iron deficiency in the United States. Morbidity and Mortality Weekly Report, 47, 1–36. Retrieved from http://www.cdc.gov/mmwr/preview/mmwrhtml/00051880.htm
- National Institutes of Health Clinical Center. (2002). Facts about dietary supplements. Retrieved from http://www.cc.nih.gov/ccc/supplements/
- National Women’s Health Information Center. (2004). Anemia.
- Retrieved from http://www.4woman.gov/faq/anemia.htm Ross, M. (2002). Evaluation and treatment of iron deficiency in adults. Nutrition in Clinical Care, 5, 220–224.
- Teresi, M. E. (2000). Iron deficiency and megaloblastic anemias. In E. T. Herfindal & D. R. Gourley (Eds.), Textbook of therapeutics: Drug and disease management (7th ed.). Hagerstown, MD: Lippincott, Williams & Wilkins.