As a nurse, I have watched many cancer patients practically stumble to their beds fatigued after taking a shower in the hospital. Most slept countless hours. Their bodies were being taxed, and potentially cured, by the harsh medications they received, and thus fatigue resulted.
There are many theories about cancer-related fatigue. One theory is that chemotherapy causes toxicity at the mitochondrial (cell energy) level, thus causing a person fatigue. Other contributing factors could be from insomnia, depression or decreased level of physical exercise. Lindsey, H. (2013, February 25). Fatigue: The Forgotten Syndrome. Oncology Times, 35(4) 26-28.
The fatigue during cancer treatment was unlike anything I had ever felt. I knew what it was like to be tired from a long 12-hour plus day at work, but this was sheer debilitating exhaustion. I went from being a physically active person, to sometimes having trouble walking down the aisles at Target. It was depressing, but that was part of the cancer journey. How I dealt with it was I slept when I needed to, and learned to put the guilt of not doing this-or-that aside.