Red blood cells carry oxygen to all parts of the body, providing the energy needed for normal activities. Chemotherapeutic agents kill all rapidly dividing cells, both cancerous and healthy, including blood cells. Chemotherapy not only destroys red blood cells, it suppresses the bone marrow's ability to produce new ones, causing anemia. The hemoglobin in red blood cells carries and releases oxygen throughout the body. Oxygen acts like fuel for the body, providing energy for muscles and organs to work.
Energy levels can plummet due to lack of oxygen-rich red blood cells.
Anti-cancer drugs doesn't keep blood cells from getting the the oxygen they need. It actually kills all rapidly dividing cells, including blood cells, and thus, not enough red cells carry oxygen around the body. To support normal movement in anemic patients, the heart tries to make up for the shortage of oxygen in the blood. It works harder to move the red blood cells more quickly and deliver oxygen faster. This increased workload can put an additional burden on the heart.