Approved by the Cancer.Net Editorial Board, 05/2023

Anemia is when the level of red blood cells in your body goes below normal. When you do not have enough red blood cells, different parts of your body are not getting enough oxygen. As a result, they cannot work the way they should and cause problems.

You can develop anemia if your body does not make enough red blood cells or destroys them. You can also develop anemia if you lose too much blood from your bloodstream. Anemia is a common side effect of cancer and many types of cancer treatment.

Treating side effects like anemia is an important part of cancer care. Talk with your health care team about any symptoms you have, including new symptoms or changes. That way, they can find and manage side effects like anemia as early as possible.

What are the symptoms of anemia?

Many people with anemia feel fatigued. Fatigue can make it harder to cope with other physical and emotional effects of cancer treatment.

Other symptoms of anemia include:

What are the causes of anemia when you have cancer?

Red blood cells are made in the body's bone marrow. Bone marrow is the soft, spongy tissue found inside larger bones. A hormone from the kidneys, called erythropoietin, tells your body when to make more red blood cells. Damage to either the bone marrow or the kidneys can cause anemia.

Anemia can be caused by cancer, cancer treatment, or related side effects. It can also be caused by factors unrelated to cancer. Common causes of anemia in people with cancer include:

Chemotherapy and other cancer drugs. Chemotherapy and other cancer drugs can damage the bone marrow. This damage is often not permanent, and anemia often improves after treatment ends.

Radiation therapy. Radiation therapy to large areas of the body can damage bone marrow. So can radiation therapy to bones in the pelvis, legs, chest, or abdomen.

Certain types of cancer. Leukemia, lymphoma, and multiple myeloma can damage bone marrow. Also, cancer that spreads to the bone or bone marrow may crowd out healthy red blood cells.

Nausea, vomiting, and loss of appetite. Nausea, vomiting, and/or appetite loss may cause you to lose nutrients. Your body needs nutrients to make red blood cells. These include iron, vitamin B12, and folic acid.

Too much blood loss. You can lose red blood cells faster than your body can make them. This may happen after surgery or if a tumor causes bleeding inside the body.

How is anemia diagnosed?

Doctors use a blood sample for a laboratory test called a complete blood count (CBC) to diagnose anemia. The CBC test result will include your number of red blood cells.

There are several ways to check your red blood cell count, including measuring hemoglobin and hematocrit. Hemoglobin is the iron-rich protein in red blood cells that carries oxygen. Hematocrit is the percentage of blood that is made up of red blood cells.

People with specific types of cancer or who are receiving certain cancer treatments may have regular CBC tests to monitor their health. In addition to anemia, a CBC looks for other blood-related problems. If your CBC shows that you have anemia, you may need other tests to find the cause.

How is anemia treated?

Doctors decide how to treat each person's anemia based on the cause of it and the symptoms they are experiencing. Treatment options include:

Blood transfusion. If anemia is causing symptoms or problems, you may need a red blood cell transfusion. During the transfusion, healthy red blood cells from a blood donor go into your body through a needle into a vein.

Medication. If chemotherapy causes anemia, your doctor may prescribe medications called erythropoiesis-stimulating agents (ESAs). ESAs are a form of erythropoietin made in the laboratory. They work by telling the bone marrow to make more red blood cells.

ESAs include epoetin alfa (Epogen, Procrit, Retacrit) and darbepoetin alfa (Aranesp). They work equally well for treating anemia from chemotherapy. They also have similar risks. Epoetin and darbepoetin are injected in the body at regular intervals. They can take several weeks to start working.

The American Society of Clinical Oncology (ASCO) and the American Society of Hematology (ASH) provide these recommendations for using epoetin and darbepoetin:

  • When ESAs may be given. ESAs may be given to treat anemia if you are recovering from chemotherapy as a treatment to manage cancer symptoms. ESAs may also be given if you have low-risk myelodysplastic syndrome (MDS) even when you are not receiving chemotherapy. MDS is a bone marrow disorder than can cause anemia.

  • When ESAs should not be given. ESAs are not recommended if you are not receiving chemotherapy or if you are receiving chemotherapy to cure cancer. You should also not receive ESAs if your hemoglobin level is 10 grams per deciliter (g/dL) or higher.

  • How ESAs are given. ESAs should be given at the lowest dose possible. The goal is to raise hemoglobin levels just enough to avoid a blood transfusion. Your doctor may lower the dose when that level is reached. They may also lower the dose if the hemoglobin level rises more than 1 g/dL within 2 weeks.

    If your hemoglobin level does not rise after 6 to 8 weeks, ESA treatment is not working. Your doctor should stop the treatment.

  • Risks of ESAs. ESAs have serious health risks. This includes an increased risk of death and blood clots. Talk with your doctor about the possible risks and benefits of using ESAs. Together, you should compare them with the risks and benefits of a red blood cell transfusion. You and your doctor should be very cautious about using ESAs if you have a high risk of blood clots.

    Risk factors for developing a blood clot from ESAs include:

    • A previous blood clot

    • Recent major surgery

    • Long periods of bed rest or limited activity, such as being in the hospital

    • Some types of chemotherapy and hormone therapy

    • Some types of treatment for multiple myeloma, especially thalidomide (Thalomid) or similar drugs

This information is based on ASCO and ASH recommendations about treatment of anemia with ESAs. Please note that this link takes you to another ASCO website.

Vitamin or mineral supplements. If a lack of nutrients causes anemia, your doctor may prescribe one or more supplements. These include iron, folic acid, or vitamin B12. These supplements are usually taken by mouth. Sometimes, you may get vitamin B12 injections or intravenous iron.

Also consider eating foods high in iron or folic acid. It may be helpful to speak with an registered dietitian. Foods high in iron include:

  • Red meat

  • Beans

  • Dried apricots

  • Almonds

  • Broccoli

  • Enriched bread and cereal

Foods high in folic acid include:

  • Asparagus

  • Broccoli

  • Spinach

  • Lima beans

  • Enriched breads and cereals

Questions to ask the health care team

Consider asking your health care team these questions about anemia before you start cancer treatment.

  • Does my cancer or cancer treatment put me at risk for developing anemia?

  • Will you test my blood to look for signs of anemia? If so, how often will I need to have this test?

  • What signs or problems of anemia should I watch for? Which ones should I tell you about right away?

  • What is causing my anemia?

  • How can my anemia be treated?

  • Who can help me understand my nutritional needs?

Related Resources

ASCO Answers Fact Sheet: Anemia (PDF)

When to Call the Doctor During Cancer Treatment

How Chemotherapy Affects People Age 65 and Older

Help People With Cancer: Donate Blood and Platelets

More Information

National Cancer Institute: Anemia and Cancer Treatment