What Is Anemia? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Anemia is a condition that develops when your red blood cell count or hemoglobin is less than normal.

The condition is often associated with being tired and weak. The reason for this is that anemia occurs when your body doesn’t have adequate healthy red blood cells. Red blood cells carry oxygen to the body’s tissues.

There are different types of anemia, including but not limited to:

Iron-deficiency anemia, which is the most common type of anemia and occurs when your blood doesn’t have enough iron to produce healthy red blood cells and hemoglobin.

This type of anemia, which is the most common and widespread nutritional disorder in the world, largely contributes to the fact that more than 30 percent of the world’s population is anemic. (9)

Red blood cells carry oxygen to the body’s tissues and remove carbon dioxide. Not having enough working red blood cells may lead to tiredness and shortness of breath.

Aplastic anemia is a blood disorder in which the body’s bone marrow — the soft tissue in the center of bones — doesn’t make enough healthy blood cells. Because of this, it is sometimes referred to as bone marrow failure.

While the condition is rare, each year between 600 and 900 people in the United States are diagnosed with aplastic anemia, although the accuracy of the epidemiological data for the United States is still being determined. (3) In Western countries, the incidence is approximately two per million per year, and estimated to be two- to threefold higher in Asia. (21)

The disorder affects men and women equally and most commonly develops in adults between ages 2 and 5, ages 20 and 25, and ages 55 and older. (4)

Sickle cell anemia is an inherited blood disorder characterized by both a deficiency of healthy red blood cells and painful episodes called sickle cell crises.

The disorder is caused by a mutation in the gene that tells the body how to make hemoglobin, a protein found in red blood cells that binds to oxygen in the lungs and carries it to tissues throughout the body.

As a result of the mutation, the body produces a defective form of hemoglobin called hemoglobin S, which causes red blood cells to sickle, or develop a crescent shape.

Sickle cells are stiff and sticky and tend to block blood flow in the vessels of the limbs and organs, causing pain and raising the risk for infection and damage.

Sickle cells also have a shorter life span than normal red blood cells, leading to an overall shortage of red blood cells and, consequently, anemia.

Pernicious anemia refers to a vitamin B12 deficiency caused by autoantibodies that interfere with vitamin B12 absorption by targeting intrinsic factor (IF), gastric parietal cells, or both. This type of anemia occurs when your body cannot absorb vitamin B12, which is needed to make healthy red blood cells and to keep the nervous system working properly. (14,22)

The condition can run in families and is an autoimmune condition. B12 deficiency from low intake can also mimic pernicious anemia as they both result in anemia from reduced available B12 for red blood cell creation. (14)

At the time it was first described, pernicious anemia was associated with continuous worsening of symptoms and even death without an available treatment. (22)

With proper treatment, people who have pernicious anemia can recover, feel well, and live normal lives.

Anemia of chronic disease is also sometimes called anemia of chronic inflammation or anemia of inflammation.

Anemia of inflammation and chronic disease is considered the second most common form of anemia after iron-deficiency anemia. (12) But the exact incidence of chronic disease anemia is not known, possibly because it’s underreported and often goes unrecognized.

This type of anemia occurs when a long-term medical condition affects your body’s ability to produce healthy red blood cells. Underlying conditions can vary and may include chronic illnesses such as cancer, infections, kidney disease, and autoimmune and inflammatory diseases like rheumatoid arthritis or lupus. Most often, the chronic disease prevents your body from effectively using iron to create new red blood cells, even if there are normal or high levels of iron stored in the body. Treatment for certain diseases can also affect red blood cell production. (12,13)

Depending on the type of anemia you have, you may experience a variety of symptoms, though there is some overlap in symptoms among the various types of anemia. The most common symptom of all anemias is weakness. Here are some other symptoms.

Iron-deficiency anemia symptoms may be mild, but as the condition advances, they can get worse and include: (11)

• Extreme fatigue
• Weakness
• Pale skin
• Chest pain, rapid heartbeat, or shortness of breath
• Headache, dizziness, or light-headedness
• Cold hands and feet
• An inflamed or sore tongue
• Brittle nails
• Odd cravings for ice, dirt, or starch
• Loss of appetite, most often in babies and kids

Aplastic anemia symptoms may be severe from the start or gradually worsen over time. They include: (5,6)

• Bleeding or bruising easily
• Heavy menstrual bleeding
• Shortness of breath
• Fatigue
• Frequent infections

Sickle cell anemia symptoms can develop in some children earlier than others and typically start after the fifth or sixth month of life. Common signs and symptoms include: (8)

• Yellowish skin, known as jaundice
• Yellowish whites of the eyes, known as icterus
• Fatigue or fussiness
• Painful swelling of the hands and feet
• Frequent infections, especially pneumonia
• Fatigue and weakness
• Episodes of pain, called sickle cell crises, which occur when sickled red blood cells block blood flow to the limbs and organs

Pernicious anemia may show similar symptoms to other anemias. But because it is caused by lack of absorption of vitamin B12, and similar to inadequate B12 intake in the diet, a severe deficiency in B12 may cause: (14)

• Tingling and numbness in hands and feet
• Muscle weakness
• Loss of reflexes
• Loss of balance
• Trouble walking
• Weakened bones, leading to hip fractures
• Neurological problems, such as confusion, dementia, depression, and memory loss
• Nausea, vomiting, heartburn, abdominal bloating and gas, constipation or diarrhea, loss of appetite, and weight loss
• Enlarged liver
• Smooth, thick, red tongue

Infants who have B12 deficiency may show the following signs and symptoms: (14)

• Poor reflexes or unusual movements like face tremors
• Difficulty feeding due to tongue and throat problems
• Irritability
• Permanent growth problems if left untreated

Anemia of chronic disease may cause similar signs and symptoms to other anemias, such as fatigue, pale skin, light-headedness, shortness of breath, rapid heartbeat, irritability, and chest pain. (12)

Red blood cells play a central role in anemia.

While white blood cells fight infection and platelets help your blood clot, red blood cells carry oxygen throughout your body.

Hemoglobin is an iron-rich protein that’s found in red blood cells. Hemoglobin is what makes it possible for red blood cells to take oxygen from your lungs and carry it to places throughout your body. Hemoglobin also takes carbon dioxide from different areas of your body and brings it to your lungs, so your lungs can get rid of it when you exhale.

Your bone marrow, which is in your large bones, produces red blood cells. But the vitamin B12, folate, and other nutrients that we get from food are needed to produce hemoglobin and red blood cells.

If you lack these vitamins and nutrients, you can become anemic. (1)

In addition to not having enough red blood cells, you can also become anemic if your body gets rid of red blood cells or if, when you bleed, your body loses red blood cells more quickly than they can be replaced. (2)

Each type of anemia is caused by something different, and each ranges from mild to severe.

Iron-deficiency anemia develops when your body doesn’t have enough iron because of blood loss, consuming inadequate amounts of iron, or having a medical condition that affects your body’s ability to absorb iron from the gastrointestinal tract. (10)

Aplastic anemia is thought to be either “acquired” or “inherited,” though the exact cause is not known.

Acquired aplastic anemia, which is more common than the inherited form, may result from:

• Toxins, including benzene (a chemical sometimes used in manufacturing and chemical synthesis), pesticides, and arsenic
• Chemotherapy and radiation therapy for cancer treatment
• Various infectious diseases, including hepatitis, HIV, and Epstein-Barr virus (a type of herpesvirus)
• Lupus, rheumatoid arthritis, or other autoimmune disorders (those in which the immune system attacks healthy cells)
• Pregnancy
• Certain drugs, including some antibiotics, immunosuppressants, and some nonsteroidal anti-inflammatory drugs (NSAIDs)
• Cancer that has spread to the bone

Causes of inherited aplastic anemia, which is rare and develops from genes that are passed down from parent to child, include:

• Fanconi anemia
• Diamond–Blackfan anemia
• Shwachman–Diamond syndrome
• Dyskeratosis congenita

Over time, severe heart issues may develop, such as arrhythmia (irregular heart beat), angina, enlarged heart, and heart failure.

While blood tests can detect low blood cell counts and the possibility of aplastic anemia, they cannot diagnose the disorder.

Diagnosis generally requires a bone marrow biopsy, in which a special needle removes a small piece of bone marrow and bone, along with blood, for examination under a microscope. (6)

Sickle cell anemia occurs when a person inherits two sickle hemoglobin genes, one from each parent.

A person who inherits a sickle hemoglobin gene from one parent and a normal hemoglobin gene from the other parent is said to have sickle trait.

People with sickle trait generally don’t have symptoms related to it, but they are at risk of developing certain medical problems, and they can pass on the sickle hemoglobin gene to their children.

Sickle cell anemia affects millions of people around the world. It’s most common in people who have ancestors from sub-Saharan Africa; regions in the Western Hemisphere (South America, the Caribbean, and Central America); Saudi Arabia; India; and Mediterranean countries, such as Turkey, Greece, and Italy. (7)

In the United States, the condition affects 90,000 to 100,000 people, and mainly affects Black Americans. (7)

The prevalence of the gene mutation that causes sickle cell is higher in areas of the world where malaria is found. Researchers have found that having the sickle cell trait offers some survival advantage against malaria.

West and Central Africa are particularly hard hit, with a form of sickle cell anemia affecting about 1 to 2 percent of all births. (7)

In the United States about 70,000 to 100,000 people have sickle cell anemia, and African Americans are affected most often, as 1 out of 365 Black American babies is born with sickle cell anemia. (8)

Pernicious anemia occurs when the body can’t absorb enough vitamin B12 from food because it lacks a protein in the stomach called intrinsic factor, caused by autoantibodies to intrinsic factor or parietal cells. If you lack intrinsic factor, there is nothing you can do to prevent pernicious anemia caused by this.

Pernicious anemia can run in families, so having family members with the condition puts you at risk.

Since people with pernicious anemia cannot effectively absorb B12, they must receive supplemental B12 through injections or very high oral doses while monitoring blood tests. (23)

In rare cases, another form of B12-related anemia, megaloblastic anemia, occurs simply because you’re not eating enough B12. In these cases, eating foods high in B12 can help the condition. Such foods include: (14)

• Beef, liver, poultry, and fish
• Eggs and dairy products
• Soy-based drinks and veggie burgers
• Breakfast cereals with added vitamin B12

B12 deficiency can also be caused by other factors and conditions, such as infections, surgery, and medicines.

Diseases such as Crohn’s and celiac can also interfere with B12 absorption.

Anemia of chronic disease can be caused by the following chronic conditions: (13)

Inflammatory diseases, which are conditions that produce an inflammatory response in the body, can cause anemia of chronic disease for several reasons:

• The inflammatory response can produce cytokines, a protein that protects the body against infection and interferes with iron processing and red blood cell production.
• Inflammation can cause internal bleeding that leads to a decrease in red blood cell count.
• Inflammation of the gastrointestinal system can interfere with the body’s ability to absorb iron from food.

Types of inflammatory disease known to cause anemia of chronic disease include:

• Rheumatoid arthritis (RA)
• Ulcerative colitis
• Crohn’s disease
• Inflammatory bowel disease
• Lupus
• Diabetes
• Degenerative joint disease

Infectious diseases can cause anemia of chronic disease if a person’s immune system’s response to the infection interferes with red blood cell production.

As with inflammatory diseases, infectious diseases can cause the immune system to release cytokines, which can interfere with the body’s ability to use iron to create red blood cells. Cytokines also can block the production and function of erythropoietin, a hormone produced by the kidneys that prompts a person’s bone marrow to produce red blood cells.

Infectious diseases known to lead to anemia of chronic disease include:

• HIV/AIDS
• Hepatitis
• Tuberculosis
• Endocarditis (heart infection)
• Osteomyelitis (bone infection)

Kidney failure in people with kidney disease can cause anemia of chronic disease if the disease interferes with the kidneys’ production of erythropoietin. Diseased kidneys also can cause the body to absorb less iron and folate, nutrients necessary to the creation of red blood cells.

People with kidney failure also might experience iron deficiency as a result of blood loss that occurs during hemodialysis.

Certain types of cancer can prompt the release of inflammatory cytokines, which interfere with erythropoietin production and the creation of red blood cells by the bone marrow. These cancers include:

• Hodgkin disease
• Non-Hodgkin lymphoma
• Lung cancer
• Breast cancer

Cancer also can harm red blood cell production if it invades the bone marrow. Moreover, cancer treatments like chemotherapy and radiation therapy can lead to anemia of chronic disease if they damage the bone marrow.

In order to determine if you have anemia, your doctor will most likely talk to you about your medical and family history, give you a physical exam, and perform the following tests: (1)

• Complete blood count (CBC). A CBC will reveal the number of blood cells in a blood sample. To determine if you have anemia, your doctor will look at your blood’s number of red blood cells (hematocrit) and hemoglobin. Doctors may have different target numbers, but normal adult hematocrit values tend to range from 40 to 52 percent for men and 35 to 47 percent for women. Target adult hemoglobin values are generally 14 to 18 grams per deciliter (g/dL) for men and 12 to 16 g/dL for women. (1)

• A test that looks at the size and shape of red blood cells, called a peripheral smear. Your doctor may run a test to determine if your red blood cells have an unusual size, shape, and color. (1)
• Additional tests. Your doctor may recommend an invasive test to gather a sample of your bone marrow if you are diagnosed with anemia. This can help determine the cause. (1)

Prognosis of Anemia

The prognosis of anemia depends on its type.

Iron-deficiency anemia

Most people with iron-deficiency anemia will fully recover. But if the underlying condition is not corrected, and chronic iron deficiency persists until the red cell count and hemoglobin levels get extremely low, it can be fatal. (15)

Aplastic anemia

While prognosis varies from person to person, the condition can be short-lived for those who develop aplastic anemia because of medications, pregnancy, low-dose radiation, or infectious mononucleosis. The condition can be life-threatening if it’s severe and lasts a long time or if treatments are not effective. (16)

For those who do not recover, they may receive a bone marrow transplant from a sibling or other matched donor; their prognosis is better than for those who receive a transplant from a donor unrelated to them. And the prognosis is increasingly reported to be favorable.

For older patients with acquired aplastic anemia, when immunosuppressive therapy is the only option, about 50 percent of people will respond well to it. (16)

People with aplastic anemia are at higher than average risk of developing leukemia. (25)

Sickle cell anemia

While there is no cure for sickle cell anemia, treatments can help with pain management and with preventing complications.

Improved treatments have given a better outlet for people with sickle cell anemia. As little as 40 years ago, almost 15 percent of children born with sickle cell anemia died before age 2, and many more died as teens. (24)

Pernicious anemia

Pernicious anemia, once it manifests, will require treatment for the duration of one’s life, yet treatment is well tolerated and the disorder should not cause significant hardship.

Some studies have shown that having pernicious anemia increases the chances of developing stomach cancer. (26)

Anemia of chronic disease

If the underlying condition that is causing anemia of chronic disease gets treated, the condition can resolve as a result. (12)

The duration of anemia depends on the type.

Iron-deficiency anemia

Iron supplements (prescribed by your physician or hematologist) taken orally can work within 3 to 10 days to increase the body’s production of red blood cells; however, it typically takes months to bring iron levels back to normal. Additionally, if the source of the iron-deficiency anemia is an underlying condition, duration would depend on if and how that is addressed. (17)

Aplastic anemia

When aplastic anemia is caused by radiation, chemotherapy, and other drugs, the condition tends to subside once treatments stop. (19)

For women who develop aplastic anemia when pregnant, the condition usually improves once they’re no longer pregnant. (19)

Sickle cell anemia

Having sickle cell anemia means having a lifelong condition because a blood and bone marrow transplant are the only cure, and a small percentage of people with the disease actually get the transplant. (8)

Pernicious anemia

While pernicious anemia is a lifelong condition, treatment can help people feel well and live normal lives. In most cases, early diagnosis and treatment can help reverse complications of pernicious anemia, such as nerve damage. (14)

Anemia of chronic disease

When the underlying condition that is causing anemia of chronic disease is treated, the condition tends to go away.

Each type of anemia will require a different type of treatment, which would depend on the specifics of your diagnosis and severity of your condition. (1)

Medication Options and Other Treatment Examples

• Growth factors, both naturally occurring and man-made, are hormones that stimulate bone marrow to make blood cells to treat aplastic anemia. Immunosuppressive drug therapy is another option.
• Severe iron-deficiency anemia may require intravenous (IV) iron therapy, blood transfusion, or injections of the synthetic hormone erythropoietin, which is normally produced by the kidneys.
• When successful, a bone marrow transplant or stem cell transplant may cure sickle cell anemia.
• B12 supplements or shots may help pernicious anemia.
• Chemotherapy or bone marrow transplantation may be needed for anemias associated with bone marrow disease.
• Oxygen, pain relievers, and oral and intravenous fluids can help reduce pain and prevent complications in sickle cell anemia.
• When low iron is caused by an inadequate diet lacking iron-rich foods, a focus on high-iron foods, such as meat, poultry, fish, beans, tofu, dried fruits, dark green leafy vegetables, and iron-fortified foods like breads and cereals, can help.
• Eating or drinking foods and drinks high in vitamin C, such as orange juice, broccoli, peppers, and more, can help your body absorb iron when you eat it. (1)

Learn More About Anemia Treatments

Prevention of Anemia

In some instances, iron-deficiency anemia can be prevented with the following methods: (18)

• Treating blood loss. For those with heavy menstrual periods or stomach issues, such as frequent diarrhea or blood in your stool, addressing the root imbalances leading to blood loss can help prevent anemia.
• Consuming foods with iron. Eating foods with high levels of iron like lean meat, chicken, dark leafy vegetables, and beans can increase iron levels.
• Ensuring enough vitamin C. Drinks and foods with vitamin C like orange juice, strawberries, and broccoli can help the body absorb iron.
• A balanced diet. Balanced diets can ensure enough iron is being consumed.
• Limiting coffee or tea with meals. If you drink coffee and tea with meals, they can make it difficult for your body to absorb iron.
• Caution with calcium pills. Because calcium can affect how your body absorbs iron, ask your doctor what the best approach is for getting both enough calcium and enough iron.

While there’s no known prevention for aplastic anemia, staying clear of insecticides, herbicides, organic solvents, paint removers, and other toxic chemicals may lower your risk. (19)

While pernicious anemia caused by a lack of intrinsic factor is not preventable, those who develop the disease because they lack B12 in their diet can potentially reduce the impact by eating foods high in B12, such as beef, eggs, fortified cereal, and more. But, ultimately, they are likely to need high-dose B12 supplementation or injections under their doctors’ guidance. (14)

When anemia is not treated, it can cause complications, including: (1)

• Extreme fatigue resulting in the inability to function
• Pregnancy complications, including premature birth
• Heart problems, such as irregular heartbeat, enlarged heart, and heart failure
• Death caused by loss of blood with sickle cell anemia

Anemia affects 1.62 billion people worldwide and disproportionately occurs in countries with limited resources. Children who are preschool age are greatly affected. Nonpregnant women have the greatest prevalence, while men experience the lowest occurrences. As the most common blood condition in the United States, anemia affects three million Americans. (20)

In some cases, B12 deficiency can be caused by conditions such as infections, surgery, medicines, and diet.

Crohn’s and celiac disease can also interfere with B12 absorption.

Anemia of chronic disease can be caused by inflammatory diseases, such as rheumatoid arthritis, ulcerative colitis, Crohn’s disease, inflammatory bowel disease, lupus, diabetes, and degenerative joint disease. (13)

Infectious diseases, such as HIV, hepatitis, tuberculosis, heart infection, and bone infection, can also lead to anemia of chronic disease.

Additionally, kidney failure and cancers, such as Hodgkin disease, non-Hodgkin lymphoma, and lung and breast cancer, can cause anemia.