During radiation therapy, the body uses a lot of energy healing itself. Stress related to your illness, daily trips for treatment, and the effects of radiation on normal cells all may contribute to fatigue.
Most people begin to feel tired after a few weeks of radiation therapy.
Feelings of weakness or weariness will go away gradually after your treatment is finished. You can help yourself during radiation therapy by not trying to do too much. If you feel tired, limit your activities and use your leisure time in a restful way. Do not feel that you have to do all the things you normally do. Try to get more sleep at night, and rest during the day if you can.