Anemia
Anemia Overview
Anemia describes the condition in which the number of red blood cells in the blood is low. For this reason, doctors sometimes describe someone with anemia as having a low blood count. A person who has anemia is called anemic.
Blood is comprised of two parts; a liquid part called the plasma and a cellular part. The cellular part contains several different cell types. One of the most important and most numerous cell types is the red blood cell. The other cell types are the white blood cells and platelets. Only red blood cells are discussed in this article. The purpose of the red blood cell is to deliver oxygen from the lungs to other parts of the body.
Red blood cells are produced through a series of complex and specific steps. They are made in the bone marrow (inner part of some bones that make most of the cells in the blood), and when all the proper steps in their maturation are complete, they are released into the blood stream. The hemoglobin molecule is the functional unit of the red blood cells and is the protein structure that is inside the red blood cells.
Even though the red blood cells (or RBCs) are made within the bone marrow, many other factors are involved in their production. For example, iron is a very important component of the hemoglobin molecule; erythropoietin, a molecule secreted by the kidneys, promotes the formation of red blood cells in the bone marrow.
The following are some key points summarizing anemia and red blood cells:
- Preventing anemia and having the correct number of red blood cells requires cooperation among the kidneys, the bone marrow, and nutrients within the body. If the kidneys or bone marrow are not
functioning, or the body is poorly nourished, then normal red blood cell count and function may be difficult to maintain.
- Anemia is actually a sign of a disease process rather than a disease itself. It is usually classified as either chronic or acute. Chronic anemia
occurs over a long period of time. Acute anemia occurs quickly. Determining whether anemia has been
present for a long time or whether it is something new, assists doctors in
finding the cause. This also helps predict how severe the symptoms of anemia may be.
- Red blood cells live about 100 days, so the body is constantly trying to replace them. In adults, red blood cell production occurs in the bone marrow. Doctors try to determine if a low red blood cell count is caused by increased blood loss or from decreased production in the bone marrow. Knowing whether the number of white blood cells has changed also helps determine the cause.
- In the United States, 2%-10% of people have anemia. Other countries have even higher rates of anemia. Young women are twice as likely to have anemia than young men because of regular menstrual bleeding. Anemia occurs in both young people and in old people, but anemia in older people is more likely to cause symptoms because they typically have additional medical problems.
- In general, there are three major types of anemia, classified according to the size of the red blood cells:
- If the red blood cells are smaller than normal, this is called microcytic anemia. The major causes of this type are iron deficiency anemia and thalassemia (inherited disorders of hemoglobin).
- If the red blood cells size are normal in size (but low in number), this is called
normocytic anemia, such as anemia that accompanies chronic disease or anemia related to kidney disease.
- If red blood cells are larger than normal, then it is called macrocytic anemia. Major causes of this type are pernicious anemia and anemia related to alcoholism.
Anemia Causes
Many medical conditions cause anemia. Common causes of anemia include the following:
- Anemia from active bleeding: Loss of blood through
heavy menstrual bleeding or,
wounds can cause anemia.
Gastrointestinal ulcers or cancers such as
cancer of the colon may slowly ooze blood and can also cause anemia.
- Iron deficiency anemia: The bone marrow needs iron to make red blood cells. Iron plays an important role in the proper structure of the hemoglobin molecule. If iron intake is limited or inadequate due to poor dietary intake, anemia may occur as a result. This is called iron deficiency anemia.
- Anemia of of chronic disease: Any long-term medical condition can lead to anemia. The exact mechanism of this process in unknown, but any long-standing and ongoing medical condition such as an infection or a cancer may cause this type of anemia.
- Anemia related to kidney disease: The kidneys release a hormone called the erythropoietin that helps the bone marrow make red blood cells. In people with chronic (long-standing) kidney disease, the production of this hormone is diminished, and this in turn diminishes the production of red blood cells, causing anemia. This is called anemia related to
chronic kidney disease.
- Anemia related to pregnancy: Water weight gain during
pregnancy dilutes the blood, which may be reflected as anemia.
- Anemia related to poor nutrition: Vitamins and minerals are required to make red blood cells. In addition to iron, vitamin B12 and folate are required for the proper production of hemoglobin. Deficiency in any of these may cause anemia because of inadequate production of red blood cells. Poor dietary intake is an important cause of low folate and low vitamin B12 levels. Strict vegetarians who do not take sufficient vitamins are at risk to develop vitamin B12 deficiency.
- Pernicious Anemia: There also may be a problem in the stomach or the intestines leading to poor absorption of vitamin B12. This may lead to anemia because of vitamin B12 deficiency known as pernicious anemia.
- Sickle cell anemia: In some individuals, the problem may be related to production of abnormal hemoglobin molecules. In this condition the hemoglobin problem is qualitative, or functional. Abnormal hemoglobin molecules may cause problems in the integrity of the red blood cell structure and they may become crescent-shaped (sickle cells). There are different types of
sickle call anemia with different severity levels. This is typically hereditary and is more common in those of African, Middle Eastern, and Mediterranean ancestry.
- Thalassemia: this is another group of hemoglobin-related causes of anemia. There are many types of thalassemia, which vary in severity. These are also hereditary, but they cause quantitative hemoglobin abnormalities, meaning an insufficient number of hemoglobin molecules is made.
- Alcoholism: Poor nutrition and deficiencies of vitamins and minerals are associated with alcoholism. Alcohol itself may also be toxic to the bone marrow and may slow down the red blood cell production. The combination of these factors may lead to anemia in alcoholics.
- Bone marrow-related anemia: Anemia may be related to diseases involving the bone marrow. Some blood cancers such as leukemia or
lymphomas can alter the production of red blood cells and result in anemia. Other processes may be related to a cancer from another organ spreading to the bone marrow.
- Aplastic anemia: Occasionally some viral infections may severely affect the bone marrow and diminish production of all blood cells. Chemotherapy (cancer medications) and some other medications may pose the same problems.
- Hemolytic anemia: The normal red blood cell shape is important for its function. Hemolytic anemia is a type of anemia in which the red blood cells rupture (known as hemolysis) and become dysfunctional. This could happen due to a variety of reasons. Some forms of hemolytic anemia can be hereditary with constant destruction and rapid reproduction of red blood cells. This destruction may also happen to normal red blood cells in certain conditions, for example, with abnormal heart valves damaging the blood cells.
- Other less common causes of anemia include medication side effects, thyroid problems, cancers, liver disease, other genetic disorders,
lead poisoning,
AIDS, and bleeding disorders. It is noteworthy that there are many other potential causes of anemia that are not included in this list and these are only some of the more common and important ones.
Anemia Symptoms
Because a low red blood cell count decreases oxygen delivery to every tissue in the body, anemia may cause many signs and symptoms. It can also make almost any other underlying medical condition worse. If anemia is mild, it may not cause any symptoms. If anemia is slowly ongoing (chronic), the body may adapt and compensate for the change; in this case there may not be any symptoms until the anemia becomes more severe.
Symptoms of anemia may include the following:
- Fatigue
- weakness
- shortness of breath
- lightheadedness
- palpitations (feeling of the heart racing or beating irregularly)
- looking pale
Symptoms of severe anemia may include:
Some of the signs that may indicate anemia in an individual may include:
- Change in stool color, including black and tarry stools (sticky and foul smelling), maroon-colored, or visibly bloody stools if the anemia is due to blood loss through the gastrointestinal tract.
- rapid heart rate
- low blood pressure
- rapid breathing
- pale or cold skin
- yellow skin called jaundice if anemia is due to red blood cell breakdown
- heart murmur
- enlargement of the spleen with certain causes of anemia
When to Seek Medical Care
Because anemia is typically a clue to another underlying disease, it needs to be fully evaluated by a doctor, and proper testing needs to be undertaken to determine the cause. Therefore, if signs and symptoms of anemia are present, one should contact his or her physician for evaluation.
- In the elderly and people with chronic medical conditions, such as
heart disease or lung disease, the symptoms of anemia may be more significant, and a prompt medical evaluation is prudent.
- The diagnosis of anemia at home is difficult unless bleeding is obvious. If significant bleeding is obvious, as in a severe injury, immediate medical attention is required and one may consider going to the emergency room. Generally, this kind of acute (short onset) anemia is more likely to cause immediate symptoms than chronic (long-lasting) types of anemia.
- Many individuals with chronic conditions, such as sickle cell anemia, know when they may be having an attack related to their disease (sickle cell crisis) and may opt to seek medical attention promptly.
Exams and Tests
Doctors can easily detect anemia by drawing a blood sample for a complete blood count. Based on the results of the test and thorough evaluation of the patient, the doctor may order more tests to determine the exact cause of anemia. The complete blood count may be done as part of a routine general check-up or based upon the presence of signs and symptoms that can be related to anemia.
Because anemia is only a symptom of a disease, doctors will want to determine what is causing the anemia. Some people may need many tests, and some people may need very few. For example, an anemic person with known stomach ulcers may not need multiple blood tests but, may need to have his or her stomach
visually evaluated and have the ulcers treated. On the other hand, a person with a family history of anemia and without an obvious source of blood loss may need multiple laboratory tests and other types of testing.
Doctors also take into consideration the severity of the anemia when deciding
the tests to order. When a person has severe anemia, the cause must be determined rapidly so that it can be treated appropriately.
Lab tests for anemia may include the following:
- Complete blood count: Determines the severity and type of anemia (microcytic anemia or small sized red blood cells, normocytic anemia or normal sized red blood cells, or macrocytic anemia or large sized red blood cells) and is typically the first test ordered.
- Stool hemoglobin test: Tests for blood in stool which may detect bleeding from the stomach or the intestines.
- Peripheral blood smear: Looks at the red blood cells under a microscope to determine the size, shape, number, and color as well as evaluate other cells in the blood.
- Iron level: An iron level may tell the doctor whether anemia may be related to iron deficiency or not. This test is usually accompanied by other tests that measure the body's iron storage, such as transferrin level and ferritin level.
- Transferrin level: Evaluates a protein that carries iron around the body.
- Ferritin: Evaluates at the total iron available in the body.
- Folate: A vitamin needed to produce red blood cells, which is low in people with poor eating habits.
- Vitamin B12: A vitamin needed to produce red blood cells, low in people with poor eating habits or in pernicious anemia.
- Bilirubin: Useful to determine if the red blood cells are being destroyed within the body which may be a sign of hemolytic anemia.
- Lead level: Lead toxicity used to be one of the more common causes of anemia in children.
- Hemoglobin electrophoresis: Sometimes used when a person has a family history of anemia; this test provides information on sickle cell anemia or thalassemia.
- Reticulocyte count: A measure of new red blood cells produced by the bone marrow
- Liver function tests:
A common test to determine how the liver is working, which may give a clue to other underlying diseases causing anemia.
- Bone marrow biopsy:
Evaluates production of red blood cells and may be done when a bone marrow problem is suspected.
Anemia Treatment
Self-Care at Home
Very little can be done to self-treat anemia, medical treatment is generally needed. It is important to continue to take any medication that is prescribed for other chronic (long-lasting) medical problems. If the reason for anemia is known, then measures to keep it under control are very important. For example, if anemia is caused by a stomach ulcer, then medications such as
aspirin or
ibuprofen should be avoided, unless otherwise directed by a doctor.
Medical Treatment
Medical treatment of anemia varies widely and depends on the cause and the severity of anemia.
If anemia is mild and associated with no symptoms or minimal symptoms, a thorough investigation by a doctor will be done in the outpatient setting (doctor's office). If any cause is found, then treatment will be started. For example, if anemia is mild and is found to be related to low iron levels, then iron supplements may be given during further investigation to determine the cause of the iron deficiency is carried out.
On the other hand, if anemia is related to sudden blood loss from an injury or a rapidly bleeding stomach ulcer, then hospitalization and transfusion of red blood cells may be required to relieve the symptoms and replace the lost blood. Further measures to control the bleeding may
occur at the same time to stop further blood loss.
Blood transfusion may be required in other less critical circumstances as well. For example, an individual who is receiving chemotherapy for a cancer may be expected by the treating physician to have bone marrow problems related to the chemotherapy. Therefore, the doctor may check blood counts routinely, and if the levels get to a low enough level, he or she may order a red blood cell transfusion to help with the symptoms of anemia.
Medications
Medications and treatments that correct the common underlying causes of anemia include the following:
- Iron may be taken during pregnancy and when iron levels are low. It is important to determine the cause of iron deficiency and treat it properly.
- Vitamin supplements may replace folate and vitamin B12 in people with poor eating habits. In people with pernicious anemia who are unable to absorb sufficient amounts of vitamin B12, monthly injections of vitamin B12 are commonly used to replete the vitamin B 12 levels and correct the anemia.
- epoetin alfa (Procrit or Epogen) injection can be used to increase red blood cell production in people with kidney problems. The production of erythropoietin is reduced in people with advanced kidney disease, as described earlier.
- Stopping a medication that may be the cause of anemia may also reverse anemia after consultation with a physician.
- If alcohol is the cause of anemia, then in addition to taking vitamins and maintaining adequate nutrition, alcohol consumption needs to be stopped.
Surgery
There are no specific surgical interventions for the treatment of anemia. However, depending on the causes of the anemia, surgery may be a treatment option. For example, if colon cancer or
uterine cancer that slowly bleeds is the cause of anemia, then surgical removal of the cancer would potentially treat the anemia.
Next Steps
Follow-up
Follow-up care for anemia will depend on its type. Most will require repeat blood counts. Also, repeat visits to the doctor's office are likely in order to determine the response to treatment.
Prevention
Some common forms of anemia are most easily prevented by eating a healthy diet and limiting alcohol use. All types of anemia are best avoided by seeing a doctor regularly and when problems arise. In the elderly, routine blood work ordered by the doctor, even if there are no symptoms, may detect anemia and prompt the doctor to look for the underlying causes.
Outlook
How well someone with anemia will recover depends on the cause of the anemia and how severe it is. For example, if a stomach ulcer is causing anemia and it can be cured, then the anemia can be cured. If anemia is caused by kidney failure, however, then it most likely will require long-term treatment.
In general, young people recover from anemia more quickly than older people do. Younger people also tolerate anemia better than elderly people because elderly people tend to have more chronic medical problems. Anemia makes almost any medical problem worse.
Synonyms and Keywords
red blood cell, red blood cells, sickle cell anemia, pernicious anemia, iron deficiency anemia, low blood count, low blood counts, tired blood, anemic, blood, dehydration, anemia
Authors and Editors
Author: Saimak T. Nabili, MD, MPH
Editor: Melissa Conrad Stöppler, MD
Previous contributing authors and editors:
Author: Patrick Yorba, MD, Staff Physician, Department of Emergency Medicine, University of Virginia Health Sciences Center.
Coauthor(s): J
Stephen Huff, MD, Associate Professor of Emergency Medicine and Neurology, Department of Emergency Medicine, University of Virginia Health System;
Mark A Mullins, MD, Staff Physician, Department of Emergency Medicine, UMASS Memorial Medical Center.
Editors: Scott H Plantz, MD, FAAEM, Research Director,
Assistant Professor, Department of Emergency Medicine, Mount Sinai School of
Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Anthony Anker, MD, FAAEM, Attending Physician, Emergency Department, Mary Washington Hospital, Fredericksburg, VA.
Last Editorial Review: 12/9/2008
