Understanding Low Red Blood Counts

Chemotherapy can cause low red blood cell counts. Understand the red blood cell tests, low red blood count symptoms, and what to do about them.

By , Caring.com senior editor
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Red blood cells are a key life force of the body, playing an essential role in carrying oxygen from the lungs to the cells. That's why when someone's red blood count drops, he really feels it -- and shows it. He may be pale, tired, weak, and have trouble catching his breath. Here's what you need to know to understand what's happening and what to do.

Why does cancer cause red blood cell (RBC) counts to drop?

  • In most cases, it's not the cancer itself but cancer treatment that leads to a shortage of red blood cells, also called anemia. Chemotherapy often damages the bone marrow that produces red and white blood cells and platelets, a condition called bone marrow suppression, or myelosuppression. As red blood cells die out, which they do naturally every 120 days or so, the body isn't able to replace them, and the red blood count drops.
  • Radiation therapy can also damage red blood cell production, particularly if the radiation targets areas such as the pelvis, where bones have more marrow and higher blood cell-generation activity.
  • Blood loss, either from surgery or from particular cancers, can also cause or exacerbate anemia. Colorectal cancers, for example, often cause blood loss as blood leaks from the intestines. Cancers that affect the blood and bone marrow, particularly lymphoma and leukemia, can also damage the production of red blood cells.