Anemia occurs when the number of red blood cells circulating in the body decreases. It is the most common blood disorder.

According to a 2015 article published in The Lancet, around one-third of the world’s population has a form of anemia.

Other health conditions, such as those that interfere with the body’s production of healthy red blood cells (RBCs) or increase the rate of the breakdown or loss of these cells, can cause anemia. Anemia can lead to symptoms including fatigue, shortness of breath, and lightheadedness.

In this article, we explain the types, symptoms, and causes of anemia, as well as the treatments available.

The most common symptom of anemia is fatigue. Other common symptoms include:

  • pallid complexion
  • a fast or irregular heartbeat
  • shortness of breath
  • chest pain
  • headache
  • lightheadedness

However, symptoms vary from person to person. Some people with mild anemia may experience few or no symptoms.

There are many forms of anemia, and each type has telltale symptoms. Some common types of anemia include:

  • iron deficiency anemia
  • vitamin B12 deficiency anemia
  • aplastic anemia
  • hemolytic anemia

Iron deficiency anemia

The most common form of anemia, iron deficiency anemia involves the body producing too few RBCs due to a lack of iron in the body. It may develop as a result of:

It can cause symptoms including:

  • fatigue
  • lightheadedness
  • cold extremities

Learn more about iron deficiency anemia.

Vitamin B12 deficiency anemia

Vitamin B12 is essential for the production of RBCs. If a person does not consume or absorb enough B12, their RBC count may be low.

Some symptoms include:

  • difficulty walking
  • confusion and forgetfulness
  • vision problems
  • diarrhea
  • glossitis, which is a smooth, red tongue

Learn more about vitamin B12 deficiency anemia.

Aplastic anemia

This rare blood condition happens when the bone marrow cannot produce enough new RBCs. It is most often a result of an autoimmune disease that damages stem cells. This occurs despite having normal iron levels.

It can cause symptoms such as:

  • fatigue
  • frequent infections
  • skin rashes
  • bruising easily

Learn more about aplastic anemia.

Hemolytic anemia

This type of anemia happens when RBCs are destroyed faster than the body can produce new ones. A variety of conditions can cause this, such as autoimmune diseases, infections, bone marrow problems, and inherited conditions such as sickle cell disease and thalassemia.

Hemolytic anemia can cause symptoms including:

Learn more about hemolytic anemia.

The body needs RBCs to survive. They transport hemoglobin, a complex protein that attaches to iron molecules. These molecules carry oxygen from the lungs to the rest of the body.

Various health conditions can result in low levels of RBCs and cause anemia.

There are many types of anemia and no single cause. In some people, it can be difficult to identify what is causing a low RBC count.

The three main causes of anemia are:

Blood loss

Iron deficiency anemia is the most common form of anemia, and blood loss is often the cause. Blood loss can lead to low levels of iron in the blood, causing anemia.

When the body loses blood, it draws water from tissues beyond the bloodstream to help keep the blood vessels full. This additional water dilutes the blood, reducing the RBC count.

Blood loss can be acute (short term) or chronic (long term).

Some causes of acute blood loss include surgery, childbirth, and trauma. However, chronic blood loss is more often responsible for anemia. Chronic blood loss may result from conditions such as a stomach ulcer, endometriosis, cancer, or another type of tumor.

Other causes of anemia due to blood loss include:

  • gastrointestinal conditions, such as hemorrhoids, cancer, or gastritis
  • the use of nonsteroidal anti-inflammatory drugs, such as aspirin and ibuprofen
  • heavy menstrual bleeding

Decreased or impaired RBCs

Bone marrow is the soft, spongy tissue at the center of bones, and it plays an essential role in creating RBCs. The marrow produces stem cells, which develop into RBCs, white blood cells, and platelets.

A number of diseases can affect the bone marrow. One of these is leukemia, a type of cancer that triggers the production of excessive and abnormal white blood cells. This disrupts the production of RBCs.

Problems with bone marrow can also cause anemia. Aplastic anemia, for example, occurs when few or no stem cells are present in the marrow.

In some cases, anemia happens when RBCs do not grow and mature as usual. This happens in people with thalassemia, a hereditary form of anemia.

Destruction of RBCs

RBCs typically have a life span of 120 days. However, the body may destroy or remove them before they complete their natural life cycle in the bloodstream.

Autoimmune hemolytic anemia is caused by the destruction of RBCs. It occurs when the immune system mistakes RBCs for a foreign substance and attacks them.

There is a range of treatments for anemia. Each aims to increase a person’s RBC count, which increases the amount of oxygen in the blood.

The required treatment depends on the type of anemia a person has. Treatments for common forms of anemia include the following:

  • Iron-deficiency anemia: Iron supplements and dietary changes can help, and a doctor will identify and address the cause of any excessive bleeding if present.
  • Vitamin deficiency anemia: Treatments can include dietary supplements and vitamin B12 injections.
  • Thalassemia: Treatments include folic acid supplements, iron chelation, and, for some people, blood transfusions and bone marrow transplants.
  • Anemia due to chronic disease: The doctor will focus on managing the underlying condition.
  • Aplastic anemia: Treatment for aplastic anemia involves blood transfusions or bone marrow transplants.
  • Sickle cell anemia: Doctors treat this with oxygen therapy, pain relief medication, and intravenous fluids. They may also prescribe antibiotics, folic acid supplements, blood transfusions, and a cancer drug called hydroxyurea.
  • Hemolytic anemia: The treatment plan may include immunosuppressant drugs, treatments for infections, and plasmapheresis, which filters the blood.

If nutritional deficiencies are responsible for anemia, eating more iron-rich foods can help.

Some foods that are high in iron include:

  • iron-fortified cereal and bread
  • leafy green vegetables, such as kale, spinach, and watercress
  • pulses and beans
  • brown rice
  • white or red meats
  • nuts and seeds
  • fish
  • tofu
  • eggs
  • dried fruits, including apricots, raisins, and prunes

Anemia can occur in people of all ages, sexes, and ethnicities. However, the following factors increase a person’s risk of developing a form of the condition:

  • being born prematurely
  • being 6–24 months old
  • menstruating
  • being pregnant and giving birth
  • consuming a diet low in vitamins, minerals, and iron
  • taking medications that inflame the stomach lining, such as NSAIDs
  • having a family history of inherited anemia
  • having an intestinal disorder that affects the absorption of nutrients
  • losing blood
  • having a chronic illness such as AIDS, diabetes, kidney disease, cancer, rheumatoid arthritis, heart failure, or liver disease

There are various ways to diagnose anemia, but the most common method involves a blood test called a complete blood count (CBC). This test measures a number of components, including:

  • hematocrit levels, which involves comparing the volume of RBCs with the total volume of blood
  • hemoglobin levels
  • RBC count

A CBC can give an indication of a person’s overall health. It can also help a doctor decide whether to check for underlying conditions such as leukemia or kidney disease.

If RBC, hemoglobin, and hematocrit levels fall below the typical range, a person likely has some form of anemia.

However, it is possible for a healthy person’s levels to fall outside this range. A CBC is not conclusive, but it is a helpful starting point for a doctor to make an accurate diagnosis.

The outlook for a person with anemia depends on its cause.

Sometimes, people can prevent or manage anemia with dietary changes alone. Other types of anemia require more significant treatment protocols, and some can be life threatening without treatment.

If a person feels continually weak and tired, they should contact a doctor for testing.

Anemia occurs when a low number of RBCs are circulating in the body. This reduces the person’s oxygen levels and can lead to symptoms such as fatigue, pale skin, chest pain, and breathlessness.

Common causes are blood loss, reduced or impaired RBC production, and the destruction of RBCs.

A doctor can use a CBC test to help detect anemia. Treatment varies depending on the type, but it may include dietary changes, supplements, medications, blood transfusions, and bone marrow transplants.