Fatigue related to radiation treatments usually starts about the second or third week of treatment, and may continue for up to 3 months or longer afterward. It is important to take good care of yourself. This means eating a well-balanced diet, drinking lots of fluid, sleeping well at night, and doing exercise as tolerated, such as walking regularly. Once you start feeling fatigued, match your activity to how you feel. You should identify the activities or tasks that you have to do, and ask someone else to do the other tasks.
First, if you are driving yourself to your radiation treatments, see if someone else can drive you to your radiation treatments when you start feeling tired.
Second, try keeping a diary of how you feel, what makes you feel more energetic, what makes you feel more tired. Don't do the more tiring activities. Rate the activities using a simple scale, such as on a scale of 0 (full of energy) to 10 (absolutely exhausted, no energy).
Third, talk with your doctor or nurse about problems that arise, or if your fatigue is severe.