When do radiation side effects like fatigue typically start after treatment?

Radiation side effects like fatigue can begin during treatment and often continue for several weeks after completion, so the timing you're experiencing aligns with what many patients report. Both radiation aftereffects and hormone therapy medications can contribute to fatigue, making it challenging to pinpoint the exact cause without professional guidance. Discussing both possibilities with your doctor next week will help create a clearer picture of what might be contributing to your low energy levels and explore potential management strategies.

I started anastrozole February 10th and radiation on April 6th. I am fine, but I am not working. I tire very easily after doing easy tasks, so I am relieved I don’t have to do much of anything.

Emily, that is a good question. My docs had me start Tamoxifen after few weeks after finishing radiation just to separate the side effects, but I am guessing it doesn’t really matter. But I will say that my fatigue from the radiation did last longer than a month after. I finished radiation in September and I think it took until mid November before I started to really get my energy back. You will get there. And even if it is the Anastrozole, maybe your body will adjust to it. I know when I first started Tamoxifen, I had horrible nausea for about a month or so and then it just went away.

I am on anastrazole and kisqali and experience fatigue. I finished radiation in July of 2025. The effects can linger for around 6 months they say.