Anemia and Cancer

15 Min Read


Anemia is a lack of red blood cells and/or the iron-rich molecule (hemoglobin) in red blood cells. Hemoglobin carries oxygen throughout the body and gives blood its red color. There are more than 100 different types of anemia, including sickle cell anemia. Many forms of anemia can be successfully treated, depending on the underlying cause. If left untreated, certain forms of anemia may be debilitating or even life-threatening. In many cases, anemia is one of the signs of another illness and is not the primary problem.

Anemia means the body’s tissue is not getting sufficient oxygen. As a result, an anemic person may experience fatigue, headaches, weakness, rapid pulse, and shortness of breath. Occasionally, the individual may have jaundice causing a yellowing of the skin or the whites of their eyes. The most common initial method for diagnosing anemia is a blood test known as a complete blood count (CBC).

Severe anemia has been associated with various forms of cancer, including cancers of the digestive system and bone marrow. The condition can occur due to bleeding or because cancer interferes with the body’s ability to make red blood cells.  Some leukemias, lymphomas, and metastatic cancers may cause anemia when cancer cells crowd out healthy blood cells.

Anemia is more often a side effect of chemotherapy and radiation therapy, which can destroy red blood cells as well as cancer cells. Certain medications can be prescribed to help increase the body’s production of red blood cells. In some cases, blood transfusions or a bone marrow transplant may be necessary.

Preventing anemia that is caused by an iron or vitamin deficiency may be as simple as a change of diet or adding supplements. But this may not be the case for individuals who are undergoing chemotherapy or radiation treatments. Their anemia may last as long as their treatments continue. Some degree of anemia may be present for many weeks or even months after cancer treatment has been completed

Other forms of anemia, such as sickle cell anemia, are genetic. These types of anemia cannot be prevented and remain with a person for life. Medications or iron supplements do not improve the quality or quantity of red blood cells in individuals with genetic anemias. 

About anemia

Anemia occurs when the number of red blood cells in the body drops below normal levels. The function of red blood cells is to carry oxygen throughout the body and to remove carbon dioxide. Hemoglobin is the protein molecule in red blood cells that carries oxygen and gives blood its red color. If the body does not have enough oxygen, the muscles and organs cannot function properly, which can lead to fatigue and other symptoms of anemia.

Red blood cells are produced in the bone marrow, which is the soft, inner part of the bones. Besides red blood cells, the bone marrow produces white blood cells, which are part of the immune system, and platelets, which help repair damaged blood vessels.

The average normal blood hemoglobin level for adults for men is 14 to 17 grams/deciliter (g/dL) and 12 to 15 g/dL for women. Anemia may be defined as a blood hemoglobin level under 12 grams/deciliter.  However, many individuals do not experience symptoms of anemia until their hemoglobin level drops below 10 g/dL especially if the decline has been gradual over weeks to months.

Anemia is not always a primary disease but can be a sign of another disease process. It can be either chronic (developing over a long period of time) or acute (rapid onset). While anemia can be linked to more than 100 causes, the three basic reasons for the condition are:

  • The body is losing red blood cells (bleeding)
  • The body is not producing enough red blood cells
  • The body’s red blood cells are being destroyed (e.g. antibodies, chemicals)

Anemia can affect individuals at any point in their lives. Hereditary forms of anemia may affect infants at birth and continue through life. It is not uncommon for teenagers to develop anemia due to their rapid growth spurts, which are accompanied by increased demand for all types of nutrients, including iron. Women in their childbearing years have an increased risk of anemia due to increased demands for iron during pregnancy and as a result of monthly menstruation (blood loss), both of which can lead to iron-deficiency anemia.

Anemia can be caused by several different types of cancer for a number of reasons. For example, anemia can be the result of blood loss due to internal bleeding, a common problem associated with digestive system cancers. Also, most forms of leukemia affect the bone marrow, as do cancers that metastasize to the bone marrow. When this happens, the blood-producing marrow is compromised and the number of blood cells drops.

Moreover, anemia can arise when cancer interferes with the organs involved in maintaining proper blood levels, such as the kidneys or spleen. In addition, people who have had active cancer for some time tend to develop what is known as “anemia of chronic disease.” This is due to decreased production of red blood cells.

While anemia can be caused directly or indirectly by cancer, often it is the result of cancer treatments. At times, cancer treatment can require major surgery. With any type of major surgery, there is always a risk for significant blood loss, resulting in anemia. In severe cases, blood transfusions may be recommended.

In addition to surgery, treatments such as chemotherapy can also lead to anemia. Chemotherapy drugs target rapidly producing cells, including those in the bone marrow that are responsible for making new blood cells. The use of chemotherapy can lead to a low number of blood cells. Anemia in these cases may develop over time and will be closely monitored by healthcare professionals.

For some advanced forms of cancer, more aggressive treatments are used, including bone marrow transplants (BMT) or peripheral blood stem cell transplants (PBSCT). In these cases, patients are given high doses of chemotherapy, possibly in combination with radiation therapy. The treatment effectively destroys nearly all of the bone marrow and halts blood cell production. Some patients undergoing BMT or PBSCT may need blood transfusions.

Diagnosis methods for anemia

Anemia is a condition caused by a shortage of hemoglobin in the blood. Hemoglobin is the part of a red blood cell that transfers oxygen from the lungs to the bodily tissues. Anemia is defined as a blood hemoglobin level under 12 grams/deciliter (g/dL). However, many individuals do not experience symptoms of anemia until their hemoglobin level drops below 10 g/dL. The slower the drop in hemoglobin, the more delayed the onset of the symptoms. Anemia can be caused by cancer itself because of the immune system’s response to the cancer cells. It also may be caused by cancer treatments that can deplete the body’s oxygen supply.

Anemia can be diagnosed with a complete blood count (CBC). A CBC is a test that measures the levels of red blood cells, white blood cells, and platelets in a person’s blood. Patients undergoing chemotherapy or radiation therapy will have their blood sampled on a regular basis to monitor the effects on the blood cells. Bone marrow samples may also be taken to monitor blood cell production.

Treatment methods for anemia

Treatment for anemia is directed at the underlying cause. If the anemia is caused by a specific deficiency, it may be treated with supplements, injections of specific vitamins, and/or increased intake of nutrient-rich foods. In iron deficiency anemia, all efforts should be made to find the source of the blood loss.

Anemia that is the result of cancer treatment is common and usually temporary. However, some types of treatments may be necessary until the body is able to produce sufficient levels of its own blood cells.

A physician may prescribe certain drugs that can help the patient’s body increase its red blood counts, which may in turn improve energy levels. The medication, which can take several weeks to work, mimics certain biochemicals that signal the Bone marrow to produce blood cells. They may not be prescribed when the anemia is not severe. For instance, chemotherapy affects the production of blood cells gradually and the body has some time to adjust. Good medical practice and cost considerations reserve these drugs for lower hemoglobin levels.

Blood transfusions may be necessary in more urgent cases, such as due to sudden loss of blood (which can occur with certain cancers) or due to leukemia.  In addition, transfusions may be given when a patient has other conditions that make a person more sensitive to anemia (e.g., heart disease), or if anemia symptoms are more severe.

A transfusion carries some risks, such as possible infections or reactions. A physician will consider the severity of the anemia as well as the overall health of the patient when considering a blood transfusion.

Prevention methods for anemia

Prevention methods for anemia depend on the type and cause of the condition. For those who are undergoing chemotherapy or radiation treatments, the anemia may last as long as the treatments continue. Some cancer patients report anemia-related fatigue lasting for several weeks or possibly months after the completion of their treatments. 

If anemia is caused by a vitamin or mineral deficiency, prevention can be as simple as eating a well-balanced diet that includes a wide variety of nutritious vegetables, including:

  • Green leafy and cruciferous vegetables
  • Fresh and dried fruits (e.g., raisins)
  • Grains (e.g., iron-fortified cereals)
  • Lean red meats
  • Eggs
  • Dried beans

For those who require an iron supplement, it is best to take it with vitamin C (as a supplement or a glass of orange juice) since vitamin C can help boost iron absorption. When taking iron supplements, it is best to avoid drinking tea with the supplement since this popular drink contains tannin. Tannin has been shown to reduce the body’s ability to absorb iron from supplements or from food. Milk and antacids are also implicated in reducing the body’s absorption of iron. It may be best to not drink milk at the same time as iron-rich foods or supplements.

Patients who are anemic should not attempt to self-treat with iron supplements. In many cases, people are told they cannot donate blood because they are anemic, and there is a popular misconception that they should start taking iron. This misconception is dangerous because too much iron can damage vital organs such as the heart.

In addition, iron supplements do not treat all types of anemias and in some cases may cause damage as with certain genetic anemias. In some people, taking supplements can mask the signs of more dangerous underlying conditions. People who think they are anemic should consult with their healthcare provider before taking any iron supplements. The exact cause of anemia should be determined before a treatment plan is established.

Questions for your doctor about anemia

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about anemia:

  • What could be causing my anemia?
  • What type of anemia do I have?
  • How severe is my anemia?
  • What is the best treatment for my condition?
  • Can I use iron supplements?
  • How often will I need blood tests to monitor my condition?
  • Am I likely to become anemic during my cancer treatments?
  • How will I know if my anemia requires immediate attention?
  • Is there a point where I may need blood transfusions?
  • Is there any way to prevent anemia during my treatments?
  • How long can I expect to be anemic?
  • If my anemia is inherited, what are the chances that I will pass it on to my children?

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Tom Perry, M.D., attended Tulane University and graduated Magna Cum Laude with a B.S. degree in Parasitology. He received his M.D. degree in 1983 from the University of Virginia School of Medicine, where he gained extensive research experience, including studies conducted through the National Institutes of Health.