A good night's sleep is important for your functioning and well-being. But too much sleep can be a problem. One side effect of cancer and cancer treatment is sleeping too much. This is called hypersomnia.
Hypersomnia is different from fatigue. Fatigue is the feeling of being tired, but able to stay awake if you try. If you have hypersomnia, you have trouble staying awake when you want to and try to. You may sleep 10 hours at night, but still can’t stay awake during the day. This sleep problem can be caused by cancer treatments or other medicines.