Most people getting radiation therapy feel fatigued. It does not mean that your cancer is getting worse. It does not mean that the treatment is not working. In fact, it is normal to feel very tired during this time.

How long does the fatigue last after radiation?

Radiation can give you fatigue that gets worse over time (called cumulative fatigue). It usually lasts 3 to 4 weeks after your treatment stops, but it can continue for up to 3 months. Hormone therapy deprives the body of estrogen, and that can lead to fatigue that may last throughout your treatment or longer.

Why does radiation make you so tired?

Most people start to feel tired after a few weeks of radiation therapy. This happens because radiation treatments destroy some healthy cells as well as the cancer cells. Fatigue usually gets worse as treatment goes on. Stress from being sick and daily trips for treatment can make fatigue worse.