Anemia (uh-NEE-me-uh) is a condition in which your blood has a lower than normal number of red blood cells.
Anemia also can occur if your red blood cells don't contain enough hemoglobin (HEE-muh-glow-bin). Hemoglobin is an iron-rich protein that gives blood its red color. This protein helps red blood cells carry oxygen from the lungs to the rest of the body.
If you have anemia, your body doesn't get enough oxygen-rich blood. As a result, you may feel tired or weak. You also may have other symptoms, such as shortness of breath, dizziness, or headaches.
Severe or long-lasting anemia can damage your heart, brain, and other organs in your body. Very severe anemia may even cause death.
Blood is made up of many parts, including red blood cells, white blood cells, platelets (PLATE-lets), and plasma (the fluid portion of blood).
Red blood cells are disc-shaped and look like doughnuts without holes in the center. They carry oxygen and remove carbon dioxide (a waste product) from your body. These cells are made in the bone marrow—a sponge-like tissue inside the bones.
White blood cells and platelets (PLATE-lets) also are made in the bone marrow. White blood cells help fight infection. Platelets stick together to seal small cuts or breaks on the blood vessel walls and stop bleeding. With some types of anemia, you may have low numbers of all three types of blood cells.
Anemia has three main causes: blood loss, lack of red blood cell production, or high rates of red blood cell destruction. These causes might be the result of diseases, conditions, or other factors.
Many types of anemia can be mild, short term, and easily treated. You can even prevent some types with a healthy diet. Other types can be treated with dietary supplements.
However, certain types of anemia can be severe, long lasting, and even life threatening if not diagnosed and treated.
If you have signs or symptoms of anemia, see your doctor to find out whether you have the condition. Treatment will depend on the cause of the anemia and how severe it is.
There are many types of anemia with specific causes and traits. Some of these include:
The three main causes of anemia are:
For some people, the condition is caused by more than one of these factors.
Blood loss is the most common cause of anemia, especially iron-deficiency anemia. Blood loss can be short term or persist over time.
Heavy menstrual periods or bleeding in the digestive or urinary tract can cause blood loss. Surgery, trauma, or cancer also can cause blood loss.
If a lot of blood is lost, the body may lose enough red blood cells to cause anemia.
Both acquired and inherited conditions and factors can prevent your body from making enough red blood cells. "Acquired" means you aren't born with the condition, but you develop it. "Inherited" means your parents passed the gene for the condition on to you.
Acquired conditions and factors that can lead to anemia include poor diet, abnormal hormone levels, some chronic (ongoing) diseases, and pregnancy.
Aplastic anemia also can prevent your body from making enough red blood cells. This condition can be acquired or inherited.
A diet that lacks iron, folic acid (folate), or vitamin B12 can prevent your body from making enough red blood cells. Your body also needs small amounts of vitamin C, riboflavin, and copper to make red blood cells.
Conditions that make it hard for your body to absorb nutrients also can prevent your body from making enough red blood cells.
Your body needs the hormone erythropoietin (eh-rith-ro-POY-eh-tin) to make red blood cells. This hormone stimulates the bone marrow to make these cells. A low level of this hormone can lead to anemia.
Chronic diseases, like kidney disease and cancer, can make it hard for your body to make enough red blood cells.
Some cancer treatments may damage the bone marrow or damage the red blood cells' ability to carry oxygen. If the bone marrow is damaged, it can't make red blood cells fast enough to replace the ones that die or are destroyed.
People who have HIV/AIDS may develop anemia due to infections or medicines used to treat their diseases.
Anemia can occur during pregnancy due to low levels of iron and folic acid and changes in the blood.
During the first 6 months of pregnancy, the fluid portion of a woman's blood (the plasma) increases faster than the number of red blood cells. This dilutes the blood and can lead to anemia.
Some infants are born without the ability to make enough red blood cells. This condition is called aplastic anemia. Infants and children who have aplastic anemia often need blood transfusions to increase the number of red blood cells in their blood.
Acquired conditions or factors, such as certain medicines, toxins, and infectious diseases, also can cause aplastic anemia.
Both acquired and inherited conditions and factors can cause your body to destroy too many red blood cells. One example of an acquired condition is an enlarged or diseased spleen.
The spleen is an organ that removes wornout red blood cells from the body. If the spleen is enlarged or diseased, it may remove more red blood cells than normal, causing anemia.
Examples of inherited conditions that can cause your body to destroy too many red blood cells include sickle cell anemia, thalassemias, and lack of certain enzymes. These conditions create defects in the red blood cells that cause them to die faster than healthy red blood cells.
Hemolytic anemia is another example of a condition in which your body destroys too many red blood cells. Inherited or acquired conditions or factors can cause hemolytic anemia. Examples include immune disorders, infections, certain medicines, or reactions to blood transfusions.
Anemia is a common condition. It occurs in all age, racial, and ethnic groups. Both men and women can have anemia. However, women of childbearing age are at higher risk for the condition because of blood loss from menstruation.
Anemia can develop during pregnancy due to low levels of iron and folic acid (folate) and changes in the blood. During the first 6 months of pregnancy, the fluid portion of a woman's blood (the plasma) increases faster than the number of red blood cells. This dilutes the blood and can lead to anemia.
During the first year of life, some babies are at risk for anemia because of iron deficiency. At-risk infants include those who are born too early and infants who are fed breast milk only or formula that isn't fortified with iron. These infants can develop iron deficiency by 6 months of age.
Infants between 1 and 2 years of age also are at risk for anemia. They may not get enough iron in their diets, especially if they drink a lot of cow's milk. Cow's milk is low in the iron needed for growth.
Drinking too much cow's milk may keep an infant or toddler from eating enough iron-rich foods or absorbing enough iron from foods.
Older adults also are at increased risk for anemia. Researchers continue to study how the condition affects older adults. Many of these people have other medical conditions as well.
Factors that raise your risk for anemia include:
The most common symptom of anemia is fatigue (feeling tired or weak). If you have anemia, you may find it hard to find the energy to do normal activities.
Other signs and symptoms of anemia include:
These signs and symptoms can occur because your heart has to work harder to pump oxygen-rich blood through your body.
Mild to moderate anemia may cause very mild symptoms or none at all.
Some people who have anemia may have arrhythmias (ah-RITH-me-ahs). Arrhythmias are problems with the rate or rhythm of the heartbeat. Over time, arrhythmias can damage your heart and possibly lead to heart failure.
Anemia also can damage other organs in your body because your blood can't get enough oxygen to them.
Anemia can weaken people who have cancer or HIV/AIDS. This can make their treatments not work as well.
Anemia also can cause many other health problems. People who have kidney disease and anemia are more likely to have heart problems. With some types of anemia, too little fluid intake or too much loss of fluid in the blood and body can occur. Severe loss of fluid can be life threatening.
Your doctor will diagnose anemia based on your medical and family histories, a physical exam, and results from tests and procedures.
Because anemia doesn't always cause symptoms, your doctor may find out you have it while checking for another condition.
Your doctor may ask whether you have any of the common signs or symptoms of anemia. He or she also may ask whether you've had an illness or condition that could cause anemia.
Let your doctor know about any medicines you take, what you typically eat (your diet), and whether you have family members who have anemia or a history of it.
Your doctor will do a physical exam to find out how severe your anemia is and to check for possible causes. He or she may:
Your doctor also may do a pelvic or rectal exam to check for common sources of blood loss.
You may have various blood tests and other tests or procedures to find out what type of anemia you have and how severe it is.
Often, the first test used to diagnose anemia is a complete blood count (CBC). The CBC measures many parts of your blood.
The test checks your hemoglobin and hematocrit (hee-MAT-oh-crit) levels. Hemoglobin is the iron-rich protein in red blood cells that carries oxygen to the body. Hematocrit is a measure of how much space red blood cells take up in your blood. A low level of hemoglobin or hematocrit is a sign of anemia.
The normal range of these levels might be lower in certain racial and ethnic populations. Your doctor can explain your test results to you.
The CBC also checks the number of red blood cells, white blood cells, and platelets in your blood. Abnormal results might be a sign of anemia, another blood disorder, an infection, or another condition.
Finally, the CBC looks at mean corpuscular (kor-PUS-kyu-lar) volume (MCV). MCV is a measure of the average size of your red blood cells and a clue as to the cause of your anemia. In iron-deficiency anemia, for example, red blood cells usually are smaller than normal.
If the CBC results show that you have anemia, you may need other tests, such as:
Because anemia has many causes, you also might be tested for conditions such as kidney failure, lead poisoning (in children), and vitamin deficiencies (lack of vitamins, such as B12 and folic acid).
If your doctor thinks that you have anemia due to internal bleeding, he or she may suggest several tests to look for the source of the bleeding. A test to check the stool for blood might be done in your doctor's office or at home. Your doctor can give you a kit to help you get a sample at home. He or she will tell you to bring the sample back to the office or send it to a laboratory.
If blood is found in the stool, you may have other tests to find the source of the bleeding. One such test is endoscopy (en-DOS-ko-pe). For this test, a tube with a tiny camera is used to view the lining of the digestive tract.
Your doctor also may want to do bone marrow tests. These tests show whether your bone marrow is healthy and making enough blood cells.
Treatment for anemia depends on the type, cause, and severity of the condition. Treatments may include dietary changes or supplements, medicines, procedures, or surgery to treat blood loss.
The goal of treatment is to increase the amount of oxygen that your blood can carry. This is done by raising the red blood cell count and/or hemoglobin level. (Hemoglobin is the iron-rich protein in red blood cells that carries oxygen to the body.)
Another goal is to treat the underlying cause of the anemia.
Low levels of vitamins or iron in the body can cause some types of anemia. These low levels might be the result of a poor diet or certain diseases or conditions.
To raise your vitamin or iron level, your doctor may ask you to change your diet or take vitamin or iron supplements. Common vitamin supplements are vitamin B12 and folic acid (folate). Vitamin C sometimes is given to help the body absorb iron.
Your body needs iron to make hemoglobin. Your body can more easily absorb iron from meats than from vegetables or other foods. To treat your anemia, your doctor may suggest eating more meat—especially red meat (such as beef or liver), as well as chicken, turkey, pork, fish, and shellfish.
Nonmeat foods that are good sources of iron include:
You can look at the Nutrition Facts label on packaged foods to find out how much iron the items contain. The amount is given as a percentage of the total amount of iron you need every day.
Iron also is available as a supplement. It's usually combined with multivitamins and other minerals that help your body absorb iron.
Doctors may recommend iron supplements for premature infants, infants and young children who drink a lot of cow's milk, and infants who are fed breast milk only or formula that isn't fortified with iron.
Large amounts of iron can be harmful, so take iron supplements only as your doctor prescribes.
Low levels of vitamin B12 can lead to pernicious anemia. This type of anemia often is treated with vitamin B12 supplements.
Good food sources of vitamin B12 include:
Folic acid (folate) is a form of vitamin B that's found in foods. Your body needs folic acid to make and maintain new cells. Folic acid also is very important for pregnant women. It helps them avoid anemia and promotes healthy growth of the fetus.
Good sources of folic acid include:
Vitamin C helps the body absorb iron. Good sources of vitamin C are vegetables and fruits, especially citrus fruits. Citrus fruits include oranges, grapefruits, tangerines, and similar fruits. Fresh and frozen fruits, vegetables, and juices usually have more vitamin C than canned ones.
If you're taking medicines, ask your doctor or pharmacist whether you can eat grapefruit or drink grapefruit juice. This fruit can affect the strength of a few medicines and how well they work.
Other fruits rich in vitamin C include kiwi fruit, strawberries, and cantaloupes.
Vegetables rich in vitamin C include broccoli, peppers, Brussels sprouts, tomatoes, cabbage, potatoes, and leafy green vegetables like turnip greens and spinach.
Your doctor may prescribe medicines to help your body make more red blood cells or to treat an underlying cause of anemia. Some of these medicines include:
If your anemia is severe, your doctor may recommend a medical procedure. Procedures include blood transfusions and blood and marrow stem cell transplants.
A blood transfusion is a safe, common procedure in which blood is given to you through an intravenous (IV) line in one of your blood vessels. Transfusions require careful matching of donated blood with the recipient's blood.
For more information, go to the Health Topics Blood Transfusion article.
A blood and marrow stem cell transplant replaces your faulty stem cells with healthy ones from another person (a donor). Stem cells are made in the bone marrow. They develop into red and white blood cells and platelets.
During the transplant, which is like a blood transfusion, you get donated stem cells through a tube placed in a vein in your chest. Once the stem cells are in your body, they travel to your bone marrow and begin making new blood cells.
For more information, go to the Health Topics Blood and Marrow Stem Cell Transplant article.
If you have serious or life-threatening bleeding that's causing anemia, you may need surgery. For example, you may need surgery to control ongoing bleeding due to a stomach ulcer or colon cancer.
If your body is destroying red blood cells at a high rate, you may need to have your spleen removed. The spleen is an organ that removes wornout red blood cells from the body. An enlarged or diseased spleen may remove more red blood cells than normal, causing anemia.
You might be able to prevent repeat episodes of some types of anemia, especially those caused by lack of iron or vitamins. Dietary changes or supplements can prevent these types of anemia from occurring again.
Treating anemia's underlying cause may prevent the condition (or prevent repeat episodes). For example, if medicine is causing your anemia, your doctor may prescribe another type of medicine.
To prevent anemia from getting worse, tell your doctor about all of your signs and symptoms. Talk with your doctor about the tests you may need and follow your treatment plan.
You can't prevent some types of inherited anemia, such as sickle cell anemia. If you have an inherited anemia, talk with your doctor about treatment and ongoing care.
Often, you can treat and control anemia. If you have signs or symptoms of anemia, seek prompt diagnosis and treatment. Treatment may increase your energy and activity levels, improve your quality of life, and help you live longer.
With proper treatment, many types of anemia are mild and short term. However, anemia can be severe, long lasting, or even fatal when it's caused by an inherited or chronic disease or trauma.
Infants and young children have a greater need for iron because of their rapid growth. Not enough iron can lead to anemia. Premature and low-birth-weight babies often are watched closely for anemia.
Talk with your child's doctor if you're feeding your infant breast milk only or formula that isn't fortified with iron, especially after the child is 6 months old. Your child's doctor may recommend iron supplements.
Children who drink a lot of cow's milk also are at risk for anemia. Cow's milk is low in the iron needed for growth.
Most of the iron your child needs comes from food. Talk with your child's doctor about a healthy diet and good sources of iron, vitamins B12 and C, and folic acid (folate). Only give your child iron supplements if the doctor prescribes them. You should carefully follow instructions on how to give your child these supplements.
If your child has anemia, his or her doctor may ask whether the child has been exposed to lead. Lead poisoning in children has been linked to iron-deficiency anemia.
Teenagers also are at risk for anemia, especially iron-deficiency anemia, because of their growth spurts. Routine screenings for anemia often are started in the teen years.
Older children and teens who have certain types of severe anemia might be at higher risk for injuries or infections. Talk with your child's doctor about whether your child needs to avoid high-risk activities, such as contact sports.
Girls begin to menstruate and lose iron with each monthly period. Some girls and women are at higher risk for anemia due to excessive blood loss from menstruation or other causes, low iron intake, or a history of anemia. These girls and women may need regular screenings and followup for anemia.
Anemia can occur during pregnancy due to a lack of iron and folic acid and changes in the blood. During the first 6 months of pregnancy, the fluid portion of a woman's blood (the plasma) increases faster than the number of red blood cells. This dilutes the blood and can lead to anemia.
Severe anemia raises the risk of having a premature or low-birth-weight baby. Thus, pregnant women should be screened for anemia during their first prenatal visits. They also need routine followup as part of prenatal care.
Women often are tested for anemia after delivery (postpartum), especially if they had:
Chronic diseases, lack of iron, and/or generally poor nutrition often cause anemia in older adults. Also, in older adults, anemia often occurs with other medical problems. Thus, the signs and symptoms of anemia might not be as clear or they might be overlooked.
Contact your doctor if you have any signs or symptoms of anemia. If you're diagnosed with anemia, your doctor may:
The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.
Researchers have learned a lot about anemia and other blood diseases and conditions over the years. This knowledge has led to advances in medical care.
Many questions remain about blood diseases and conditions, including anemia. The NHLBI continues to support research aimed at learning more about these illnesses.
For example, NHLBI-supported research on anemia includes studies that explore:
Much of this research depends on the willingness of volunteers to take part in clinical trials. Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions.
For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.
By taking part in a clinical trial, you may gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.
If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.
If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.
For more information about clinical trials related to anemia, talk with your doctor. You also can visit the following Web sites to learn more about clinical research and to search for clinical trials:
For more information about clinical trials for children, visit the NHLBI's Children and Clinical Studies Web page.
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.