The causes of fatigue

Identified causes of cancer fatigue include:

The cancer itself, as some tumors compete with the body for nutrients
Low blood counts, often triggered by cancer medications
Surgery
Nutrition issues
Sleep problems
Reduced activity levels
The presence of other side effects, such as pain, infection, nausea and vomiting, and anemia
Deficiencies in key electrolytes in the body, like magnesium, potassium and sodium, usually caused by cancer-related medications
Radiation
Immunotherapy medications like Interferon/Interleukin
Other health conditions not directly related to cancer, such as thyroid problems
For some, emotional factors such as anxiety, depression and family conflict may contribute to fatigue.