“Why does radiation cause fatigue?”

Therapeutic radiation achieves its beneficial effects by killing cancer cells. Cancer cells do not have the ability to repair the damage to their DNA caused by radiation. Normal body cells are also damaged by radiation, but they can repair their DNA. This repair process takes metabolic energy. Therefore, while your body cells are repairing the damage caused by radiation, you will feel tired. Some body tissues are especially susceptible to radiation injury; for example, the lining of the digestive system. These damaged cells will be replaced rather than repaired, which also takes energy.

The level of radiation one experiences from imaging studies does not cause fatigue.

Sincerely,

Clay Hinrichs, MD