The Surprising Link Between Cancer and Anemia

There are links between anemia and colon cancer.
There are links between anemia and colon cancer. BSIP/UIG/Getty Images

Cancer and anemia are linked in a number of ways. For those suffering with colon cancer, anemia may be one of the first signs of the disease, and for those already diagnosed, anemia may be a result of cancer treatment. For example, anemia is the direct result of chemotherapy used to treat the colon cancer. Cancer-related anemia is not a disease, but it is something that may require attention. Menstruating, pregnant, and breastfeeding women may occasionally suffer anemia, which is normal and expected.

However, if your blood counts are low and you don't have a known source of bleeding or a history of anemia, you may want to speak to your doctor about screening for colon cancer.

What is Anemia?

Anemia is a deficit of red blood cells or their oxygen-transporting capacity. Iron deficiency anemia results when your body does not have enough hemoglobin, a protein in your blood, to transport oxygen. This is why shortness of breath is sometimes associated with anemia, as the lack of hemoglobin to transport oxygen throughout your body makes it harder to breathe.

Causes in People Without a Diagnosis of Cancer

  • Blood loss - from large volumes of blood, such as following a surgical procedure or during menstruation, to microscopic loss, including chronic ulcers, polyps, hemorrhoids, or bleeding from the gastrointestinal tract
  • Dietary deficit - you may not be eating enough iron rich foods
  • Inability to absorb the iron you eat - malabsorption can be the result of chronic intestinal diseases, such as Crohn's, or a result of chronic diarrhea (your body cannot absorb the iron fast enough)
  • Cancer can cause anemia in different ways. Some cancers, especially cancers of the colon and GI tract, can slowly bleed. Other cancers, like lymphoma, cause anemia by replacing the bone marrow cells that make red blood cells. Finally, some cancers slow the production of red blood cells by the bone marrow through high levels of cytokines.

    However, it is important to remember that while these are the most common causes of anemia, there are other potential causes including chronic kidney disease and vitamin deficiencies, such as a lack of folate and B12. If your blood work is showing a deficiency, your doctor will help you explore and find the root cause of your anemia.

    Causes of Anemia in Colon Cancer Patients

    More commonly with right-sided colon cancer, iron deficiency anemia may be the first thing you experience. Because the right side of your colon is distant to your rectum, blood in the stool has time to degrade and probably will not be recognizable by the time you pass it in a bowel movement. Large tumors in this portion of the colon can continue to bleed slowly, and over time, this will be reflected in a low blood count. Remember, anemia does not cause colon cancer, but it can be an indication of the disease.

    Anemia and Chemotherapy Treatment

    Anemia can also result from your chemotherapy treatments designed to cure the colon cancer.

    Almost all of the chemotherapy drugs used to treat colon cancer in the FOLFOX (fluorouracil/5-FU, leucovorin and oxaliplatin) regimen list decreased blood counts as a common side effect.

    Getting Diagnosed

    Anemia might be accompanied by symptoms that reflect your body's deficit of red blood cells, including:

    • Feeling weak or tired all of the time
    • Shortness of breath (not related to a history of asthma or a cardiac condition)
    • Increased susceptibility to infection
    • Cold hands or feet
    • Pallor (most easy to see in the mucous membranes)
    • Pica (feeling the need to eat items that are not meant as food, such as dirt)

    However, it's important to note that not everyone who is anemic suffers symptoms. Although it is mostly unfounded, some folklore says that people who chew on ice may have iron deficiency anemia.

    If you are suffering one or more of these symptoms, especially if you have a known family history of colon cancer, do not delay speaking to your doctor. He or she may be able to put your fears to rest with a simple blood test.


    If you are suffering anemia as a result of your treatment, your doctor might suggest holding or stopping your chemotherapy until your body can renew its supply of red blood cells. If this is taking too long — or if you have a dangerously low blood count — you might require a blood transfusion. Some doctors prescribe injectable medications that help your body naturally produce more blood cells, but this may require more frequent trips to the oncologist's office.

    If your doctor tells you to incorporate more iron-rich foods into your diet, consider these choices:

    • Liver (chicken or beef)
    • Red meat
    • Iron fortified cereals
    • Legumes

    Talk to your doctor about dietary changes that can help you increase your iron levels if you have any questions, and never start taking supplements, such as iron tablets, without discussing it first.


    American Cancer Society. (n.d.). Colorectal Cancer Facts and Figures 2011 - 2013. Accessed online May 17, 2013.

    Office of Dietary Supplements National Institute of Health. (n.d.). Iron: Dietary Supplement Fact Sheet for the Health Professional. Accessed online May 18, 2013.

    Raje D., et al. (August 2007). What Proportion of Patients Referred to Secondary Care with Iron Deficiency Anemia Have Colon Cancer? Disorders of the Colon & Rectum;50(8):1211-4. Accessed online May 19, 2013.

    Susman, Ed. (April 2005). Anemia Worsens Prognosis for Colorectal Cancer. Oncology Times; 7, 96. Accessed online May 17, 2013.

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