Fatigue is described as tiredness, weakness, lack of energy, or decreased physical ability. Although no one is sure exactly what causes fatigue, we do know it can be brought on by cancer and cancer treatment. Some possible causes of fatigue include:

• Medications
• Body using extra energy to repair healthy tissue after treatment
• Toxic substances released by dying cancer cells
• Infection
• Treatment-related changes to the nervous system
• Side effects or symptoms including anemia (decreased red blood cells), fever, nausea, vomiting, diarrhea, pain, breathing difficulties, lack of sleep, poor quality of sleep
• Changes in nutrition or nutritional needs
• Lack of exercise
• Emotional factors including depression, anxiety, and fear
• Diseases not related to cancer (e.g., heart, lung, musculoskeletal, etc)
• Post-cancer fatigue

It is important to let your doctor know about your fatigue; he or she may want to evaluate it. Be as specific as possible about your level of fatigue and when it occurs (e.g., in the morning, after treatment, etc.)