What Is Anemia?
Anemia (uh-NEE-me-eh) 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 (HEE-muh-glow-bin).
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
(eh-RITH-ro-sites). RBCs are disc-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.
Outlook
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.
Other Names for Anemia
- Iron-poor blood
- Tired blood
There are many types of anemia with specific causes
and characteristics. Some of these include:
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
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?
Populations Affected
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 fluid portion (plasma) 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:
- Poor or inadequate diets that are low in iron,
vitamins, and minerals
- Blood loss from surgery or injury
- Chronic or serious illnesses, such as kidney
disease, cancer, diabetes, rheumatoid arthritis, HIV/AIDS, inflammatory bowel
disease (including Crohn’s disease), liver disease, and thyroid
disease
- Chronic infections
- Family history of inherited anemia, such as
sickle
cell anemia or
thalassemia
What Are the 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:
- Shortness of breath
- Dizziness
- Headache
- Coldness in the hands and feet
- Pale skin
- Chest pain
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.
How Is Anemia Diagnosed?
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.
Physical Exam
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 hemoglobin level. Hemoglobin is the iron-rich
protein in red blood cells (RBCs) that carries oxygen through the body. The
normal range of hemoglobin levels for the general population is 11–15
g/dL. A low hemoglobin level means a person has anemia.
- The hematocrit (hee-MAT-oh-crit) level. The
hematocrit level measures how much of the blood is made up of RBCs. The normal
range for hematocrit levels for the general population is 32–43 percent. A
low hematocrit level is another sign of anemia.
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:
- The number of RBCs. Too few RBCs means a person
has anemia. A low number of RBCs is usually seen with either a low hemoglobin
or a low hematocrit level, or both.
- The number of white blood cells. White blood
cells are involved in fighting infection.
- The number of platelets in the blood. Platelets
are small cell fragments that are involved in blood clotting.
- RBC size. The mean cell volume measures the
average size (volume) of RBCs. In iron deficiency anemia, the RBCs are usually
smaller than normal. This is called microcytosis (MIKE-ro-si-TO-sis).
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:
- Hemoglobin electrophoresis (e-lek-tro-FOR-e-sis).
This test evaluates the different types of hemoglobin in the blood. The
hemoglobin electrophoresis test is used to diagnose types of anemia caused by
abnormal hemoglobin in the RBCs.
- Reticulocyte (re-TIK-u-lo-site) count.
Reticulocytes are young RBCs. This test measures the number of new RBCs in your
blood. The reticulocyte test is used to determine whether your bone marrow is
producing RBCs at the proper rate. A higher than average count usually
indicates either blood loss or destruction of RBCs earlier than their normal
life of 120 days. A lower than average count indicates a decreased production
of RBCs by the bone marrow. People with
pernicious
anemia have low reticulocyte levels.
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.
How Is Anemia Treated?
Goals of Treatment
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.
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:
- Spinach and other dark green, leafy
vegetables
- Peanuts, peanut butter, and almonds
- Eggs
- Peas; lentils; and white, red, or baked
beans
- Dried fruits, such as raisins, apricots, and
peaches
- Prune juice
Vitamin C
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.
Vitamin B12
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
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:
- Spinach and other dark green, leafy vegetables
(folate comes from the Latin work meaning “leaf”)
- Black-eyed peas or dried beans
- Beef liver
- Eggs
- Bananas, oranges, orange juice, and some other
fruits and juices
Medicines
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:
- Antibiotics to treat infections.
- Hormone treatment for adult and teenaged women
who have heavy menstrual bleeding.
- Epoetin—a man-made version of
erythropoietin, a hormone made by the kidneys that stimulates increased
production of RBCs. This medicine has some risks. Based on your situation, your
doctor will decide whether the benefits of the medicine outweigh the risks.
- Medicines to prevent the body’s immune
system from mistakenly attacking its own RBCs.
- Chelation (ke-LAY-shun) therapy for lead
poisoning (mainly in children).
Medical Procedures
Some types of serious anemia may require medical
procedures. These procedures include blood transfusions and transplants of bone
marrow or stem cells.
Blood Transfusions
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
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.
How Can Anemia Be Prevented?
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 followup
should be done for girls and women at increased risk for anemia due to:
- Excessive blood loss from menstruation or other
causes
- Low iron intake
- A history of anemia
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 followup 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:
- During pregnancy, the woman had anemia that
continued during the last 3 months (third trimester) of pregnancy.
- The woman had excessive blood loss during
pregnancy, childbirth, or after childbirth.
- The woman had a multiple birth.
Older Adults
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.
- For anemia resulting from cancer or kidney
disease, or from treating those illnesses, your doctor may prescribe epoetin
(the man-made form of the hormone erythropoietin that stimulates formation of
RBCs in bone marrow).
- Your doctor also may prescribe iron, vitamin, or
folic acid supplements.
Key Points
- 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. Without enough RBCs or hemoglobin, the blood
does not carry enough oxygen to the rest of the body.
- Anemia is caused by blood loss, lower than normal
levels of RBC production, or higher than normal rates of RBC destruction.
- The lack of oxygen causes people with anemia to
feel tired and weak. Other symptoms of anemia include shortness of breath,
dizziness, fast or irregular heartbeat, headache, coldness in the limbs, pale
or yellow skin, and chest pain.
- Anemia is a common condition affecting more than
3 million people in the United States. Women and people with chronic diseases
are at greater risk for anemia. People who have symptoms of anemia should see
their doctor to diagnose its cause and severity and to develop an effective
treatment plan.
- Anemia is diagnosed using a person’s medical
and family history, a physical exam, and tests. A complete blood count often is
used to confirm a diagnosis of anemia. Additional tests may be needed to
determine the cause and severity of anemia so that an effective treatment can
be prescribed.
- Anemia can often be treated and/or controlled.
Treatment may lead to benefits such as increased energy and activity levels,
improved quality of life, and longer life.
- Some types of anemia may be severe, long lasting,
and life threatening if not diagnosed and treated. The lack of oxygen in the
body can damage organs. Anemia can harm the heart, which works harder to make
up for the lack of blood cells or hemoglobin.
- Many types of anemia can be treated effectively
with diet supplements that increase the level of iron and its absorption into
the blood.
- Some forms of anemia can be prevented by a
healthy diet rich in the vitamins and minerals, especially iron, that are
needed to produce RBCs and hemoglobin.
- Some types of anemia are inherited and can’t
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.
Links to Other Information About Anemia
NHLBI Resources
Non-NHLBI Resources
Clinical Trials
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