Anemia is a condition in which a person's blood has a lower than normal number of red blood cells (RBCs), or the RBCs don't have enough hemoglobin. Hemoglobin – an iron-rich protein that gives the red color to blood – carries oxygen from the lungs to the rest of the body. In people with anemia, the blood does not carry enough oxygen to the rest of the body. As a result, people with anemia feel tired, along with other symptoms, because their bodies are not receiving enough oxygen. In severe or prolonged cases of anemia, the lack of oxygen in the blood can cause serious and sometimes fatal damage to the heart and other organs of the body.
RBCs also are called erythrocytes. RBCs are disk-shaped and look like doughnuts without a hole in the center. They are produced continually in the spongy marrow inside the large bones of the body and normally last 120 days. RBCs' main role is to carry oxygen, but they also remove carbon dioxide (a waste product) from cells and carry it to the lungs to be exhaled. White blood cells and platelets are the two other kinds of blood cells. White blood cells help fight infections. Platelets help blood to clot. In some kinds of anemia, there are low amounts of all three types of blood cells.
Women and people with chronic diseases are at greater risk for anemia. Many types of anemia can be mild, short-lived, and easily treated. Some forms of anemia can be prevented with a healthy diet, and other forms can be treated with diet supplements.
Certain types of anemia may be severe, long-lasting, and life threatening if not diagnosed and treated. People who have symptoms of anemia should see their doctor to find out if they have the condition, its cause and severity, and how to treat it.
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 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.
Who is at risk for anemia?
Anemia is a common condition. More than 3 million people in the United States have anemia, and it occurs in all age groups and in all racial and ethnic groups. Both men and women can have anemia; however, women of childbearing age are more at risk for anemia than men. Women in this age range lose blood from menstruation and childbirth.
During pregnancy, anemia can develop due to deficiencies of iron and folate and from a change in the concentration of blood. During the first 6 months of pregnancy, the plasma (fluid portion) of a woman's blood increases faster than the number of red blood cells, diluting the blood and causing the hematocrit level to fall.
Older adults who have other medical conditions and infants younger than 2 years also are at increased risk for anemia.
Major risk factors
Factors that increase the risk of anemia include:
Signs and symptoms of anemia
The most common symptom of anemia is fatigue (feeling tired or weak). It may be more difficult to find the energy to do normal activities if you have anemia. Other signs and symptoms of anemia include:
All of these signs and symptoms can occur because your heart has to work harder to pump more oxygen-rich blood through the body.
In some cases of anemia, a rapid or irregular heartbeat (arrhythmia) may occur. Over time, this arrhythmia can damage your heart, causing it to enlarge and possibly resulting in heart failure. Anemia can damage other organs in your body because the blood cannot deliver enough oxygen to them.
Anemia can result from some diseases, and it can make other diseases worse. For example, some cancer treatments may damage the bone marrow that makes red blood cells or damage these cells' ability to carry oxygen. This makes the cancer patient weaker and less able to respond to treatment. People who have HIV/AIDS may develop anemia from the infection or medicines used to treat the disease. Anemia can make it more difficult for these people to respond to other medicines.
Anemia can have many other effects. People with anemia who lose blood in a serious accident or surgery are more likely to need a blood transfusion. People who have kidney disease and anemia are more likely to have trouble with their hearts. In some types of anemia, dehydration (too little fluid intake or too much loss of fluid in the blood and body) can develop. Severe dehydration can be life threatening.
Anemia is diagnosed using a person's medical history, a physical exam, and tests. Your doctor can use these methods to determine the cause, severity, and treatment for the particular type of anemia you may have. Mild to moderate anemia may have no symptoms or very mild symptoms. In fact, anemia is often discovered unexpectedly on blood tests looking for other conditions.
Medical and family history
Your doctor may ask detailed questions about many symptoms common to anemia, including feeling tired and weak. You may be asked if you've had an illness or condition that could cause anemia and whether you are taking medicines that could cause anemia. Your doctor may ask about your diet and whether you have family members who have anemia or a history of anemia.
Your doctor will do a physical exam to determine how severe the anemia is and to check for possible causes. This exam may include listening to the heart for a rapid or irregular heartbeat, listening to the lungs for rapid or uneven breathing, or feeling the abdomen to check the size of your liver and spleen. The doctor may perform a pelvic or rectal exam to check for common sources of blood loss.
Diagnostic tests and procedures
Your doctor may order various tests or procedures to determine the type and severity of anemia you have. Usually, the first test used to diagnose anemia is a complete blood count (CBC). The CBC tells a number of things about a person's blood, including:
The normal range of these levels may be lower in certain racial and ethnic populations. Your doctor can explain your individual test results.
The CBC also checks:
If the CBC results confirm that you have anemia, your doctor may order additional tests to determine the cause, severity, and correct treatment for your condition. Some of the tests may include:
Several tests can be used to check the level of iron in your blood and body. These tests include serum iron, serum ferritin, transferrin level, or total iron-binding capacity. Because anemia has many causes, the doctor may order tests for conditions such as kidney failure, lead poisoning (in children), and deficiencies of vitamins (B12, folate).
If your doctor suspects that you have anemia because of internal bleeding in your stomach or intestines, several tests may be used to discover the source of the bleeding. A test to check the stool for blood may be done in the doctor's office. Your doctor can give you a kit to help you obtain a sample at home. Your doctor will instruct you to bring the sample back to his or her office or send it to a lab.
If blood is found in the stool, additional tests may be used to find the source of the bleeding. One such test is endoscopy. In this test, a tube with a tiny camera is used to view the lining of the digestive tract.
In some cases, your doctor may want to do a bone marrow aspiration or biopsy. A bone marrow biopsy is a minor surgical procedure to remove a small amount of bone marrow tissue. Bone marrow aspiration or biopsy test whether your bone marrow is healthy and making enough blood cells. For a bone marrow aspiration, your doctor removes a small amount of bone marrow fluid through a needle.
The goal of treating anemia is to increase the oxygen-carrying capacity of the blood. This is done by increasing the red blood cell (RBC) count and/or hemoglobin level in the RBCs as close as possible to normal levels. An additional goal is to treat the underlying condition or cause of the anemia.
The treatment your doctor prescribes will depend on the type, cause, and severity of the anemia you have. Treatment may include dietary supplements, changes in diet, medicines, and/or medical procedures such as blood transfusions or surgery.
Nutrition and dietary supplements
Some types of anemia are caused by low levels of vitamins or iron in the body. Low levels of vitamins or iron can be due to poor diet or certain diseases and conditions. Treatment for vitamin or iron deficiency may include changing your diet or taking vitamin or iron supplements. The vitamin supplements most commonly taken are vitamin B12 and folate. Vitamin C is sometimes given to help the body absorb iron.
Your body needs iron to produce hemoglobin. Iron found in meats is more easily absorbed into your blood than the iron found in vegetables and other foods. To treat your anemia, your doctor may recommend eating more meat – especially red meat such as beef and liver – as well as chicken, turkey, pork, fish, and shellfish.
Sometimes iron is given in the form of mineral supplements. Usually these are combined with multivitamins and other minerals that help your body absorb iron. Some foods are fortified with extra iron (that is, iron is added to the foods). These foods include cereals, bread, and pasta. You can find out how much iron is in your food by reading the nutrition labels on food packaging. The amount is given as a percentage of the recommended daily requirement.
Other foods that are good sources of iron include:
Vitamin C helps the body absorb iron. Good dietary sources of vitamin C are vegetables and fruits, especially citrus fruits. Fresh and frozen fruits, vegetables, and juices usually have more vitamin C than canned ones. Citrus fruits include oranges, grapefruits, tangerines, and similar fruit. If you are taking medicines, ask your doctor or pharmacist whether you can eat grapefruit or drink grapefruit juice. This citrus fruit affects the strength and effectiveness of a few medicines. Other fruits rich in vitamin C include kiwi fruit, mangos, apricots, strawberries, cantaloupes, and watermelons.
Vegetables rich in vitamin C include broccoli, peppers, tomatoes, cabbage, potatoes, and leafy green vegetables like romaine lettuce, turnip greens, and spinach.
Low levels of vitamin B12 can lead to a type of anemia called pernicious anemia. Pernicious anemia most often occurs because the body is unable to absorb vitamin B12. Pernicious anemia can often be treated with vitamin B12 supplements. Good food sources of vitamin B12 include breakfast cereals fortified with this vitamin. Animal products are particularly rich in vitamin B12. These items include meats (such as beef, liver, poultry, fish, and shellfish), eggs, and dairy products (such as milk, yogurt, and cheese).
Folate is a form of vitamin B that is found in foods. Your body needs folate to produce and maintain new cells. Folate is very important for pregnant women to help avoid anemia and ensure the healthy development of the fetus. Good sources of folic acid – in addition to bread, pasta, and rice fortified with a man-made version of folate – include:
In addition to iron and vitamins, your doctor may prescribe other medicines to treat the underlying causes of anemia or to increase the production of RBCs. Some of these medicines include:
Some types of serious anemia may require medical procedures. These procedures include blood transfusions and transplants of bone marrow or stem cells.
Transfusions are given through a vein and require careful matching of donated blood with the recipient's blood. The transfused blood must be compatible at least with the recipient's blood type (A, AB, B, or O) and usually with other factors. People who receive blood transfusions on a regular basis must be monitored for iron overload – too much iron in the body. If too much iron accumulates, the person must have chelation therapy to reduce the excess iron that could cause damage to their organs.
Bone marrow or stem cell transplant
Serious anemia, such as aplastic anemia, that results from the failure of bone marrow to make RBCs is sometimes treated with marrow or stem cell transplants. Donor marrow is usually taken from a large bone, such as the pelvis. Marrow is given by transfusion through a vein. Stem cells for a transplant can be from matched umbilical cord blood, from bone marrow donated by a family member, or from a matched but unrelated donor. Stem cells in bone marrow develop into mature blood cells.
Surgery may be necessary to control or stop serious or life-threatening bleeding that is causing anemia. For example, surgery may control chronic bleeding from a stomach ulcer or colon cancer.
Removal of the spleen may be necessary to stop or reduce high rates of RBC destruction. The spleen removes worn-out RBCs from the body. An enlarged or diseased spleen removes more RBCs than normal, causing anemia.
Many kinds of anemia, especially those caused by deficiencies of iron or vitamins, may be prevented from recurring by eating a diet rich in those nutrients or by taking the appropriate supplements.
Other kinds of anemia can be prevented – or prevented from occurring again – by treating the underlying cause, such as internal bleeding, or by changing a medicine that is causing the anemia.
Most kinds of anemia can be prevented from becoming serious by reporting the signs and symptoms to your doctor. It is important to have the appropriate tests for diagnosis and to follow specific directions for treatment.
Some forms of hereditary anemia, such as sickle cell anemia, cannot be prevented. If you have a form of hereditary anemia, it is important that you discuss your personal and family history with your doctor so that timely treatment can begin.
Living with anemia
Anemia can often be treated and/or controlled. Treatment may lead to benefits such as increased energy and activity level, improved quality of life, and longer life. It is very important to seek prompt diagnosis and treatment if you have signs and symptoms of anemia.
With treatment, acute anemia may last only a day or a short time. If anemia is due to a chronic or inherited disease, the effects can be ongoing or lifelong. Severe anemia or ongoing anemia that is untreated can be life threatening.
Children and teenagers with anemia
Because of their rapid growth and development, infants and young children have a greater need for iron. Screening for anemia is recommended for preterm and low-birth-weight babies less than 6 months of age.
If your child has anemia, his or her doctor should inquire about possible exposure to lead and provide guidance about a healthy diet. Parents should talk with their child's doctor or health care provider about a healthy diet and adequate sources of iron, vitamins B12 and C, and folate. Iron supplements should be given only if they are prescribed, and directions for giving supplements should be followed carefully. Fad foods and diets should be avoided.
Teenagers also are at risk for anemia, especially iron-deficiency anemia, because of their growth spurts. Routine screenings for anemia should begin in adolescence and be done at least every 5–10 years. Older children and teens with certain types of severe anemia may be more susceptible to injury or infections. Your child's doctor can advise about restrictions, such as not taking part in contact sports.
In addition, girls begin to menstruate and lose iron with each monthly period. Annual screenings for anemia and appropriate follow-up should be done for girls and women at increased risk for anemia due to:
Medical care for pregnant and post-childbirth women
During pregnancy, anemia can develop due to deficiencies of iron and folate and from a change in the concentration of the blood. During the first 6 months of pregnancy, the fluid portion (plasma) of a woman's blood increases faster than the number of red blood cells (RBCs), diluting the blood and causing the hematocrit level to fall.
Pregnant women should be screened for anemia at the first prenatal visit and receive routine follow-up as part of ongoing prenatal care. Severe anemia increases the risk of having a preterm birth and a low-birth-weight baby.
Women should be tested for anemia 4–6 weeks after delivery (postpartum), particularly if:
Anemia in older adults is often caused by chronic disease, iron deficiency, and/or generally poor nutrition. Although anemia in older adults usually occurs with other medical problems, the signs and symptoms are often nonspecific and may be overlooked.