Cancer
Fatigue See All Managing Cancer-Related Fatigue in Fatigue Fatigue can come and go or stay constant for a while. Fatigue from chemotherapy tends to happen a few days after the treatment, peaks, and then gets better before the next treatment. Fatigue from radiation may not happen right away. ...more Fatigue: Definition in Fatigue Fatigue is a feeling of being tired, weak, or exhausted. It's the most common side effect of cancer and cancer treatment. ...more