Why Does Cancer Cause Fatigue?

Cancer-related fatigue (CRF) is a condition that can be caused by cancer and/or cancer treatment. Unlike the moderate fatigue you may feel after a busy day, cancer-related fatigue is severe. Many people report that it feels “paralyzing.” 

CRF, which is also referred to as chronic fatigue syndrome, typically comes on quickly, isn’t the result of physical activity or exertion, and doesn’t resolve with rest or sleep.  

Causes of Cancer-Related Fatigue

It’s common to experience extreme tiredness with cancer or cancer treatment. As much as 80% to 100% of people who have cancer develop this condition.  

Doctors and researchers don’t know the exact cause of cancer-related fatigue. One factor may be that cancer cells, like all cells, consume nutrients, which means some of the energy from the meals you eat isn’t available for normal body functions. 

People who are being treated for cancer also experience CRF, which may be caused by:

• Changes in how cells function
• Dehydration that results from nausea and vomiting or decrease water intake
• Changes in hormone levels
• Inflammation
• Tissue and cell damage
• Anemia from reduced red blood cell counts

So, while cancer treatment can help slow or stop the progression of the disease, cancer weakness is a significant side effect.

Cancer-Related Fatigue Diagnosis

This condition is primarily diagnosed by a patient reporting cancer fatigue symptoms. In addition to feeling extremely tired in general, a person with CRF may experience stiff shoulders, trouble concentrating, sleepiness, boredom, anxiety, or irritability.

If you think you’re suffering from cancer-related fatigue, your doctor may have you complete a questionnaire and/or keep a journal of your fatigue level. They may also order blood tests to check for issues like infections and anemia.  

Cancer-Related Fatigue Management and Treatment

The vast majority of cancer patients will experience cancer-related fatigue at some point. However, if you have cancer, there are steps you can take to reduce or prevent it. This includes:

• Exercising regularly
• Eating a healthy diet
• Managing your stress
• Conserving energy by limiting unnecessary tasks
• Being treated for anemia or hypothyroidism if appropriate
• Getting cognitive therapy

CRF Outlook

The degree and duration of extreme tiredness from cancer varies based on the type of cancer treatment a person receives. For example, cancer medications can cause fatigue that occurs during treatment but resolves between treatments. People who have cancer surgery tend to experience CRF until they recover from the procedure. 

Radiation therapy causes fatigue that increases as the treatment progresses but tends to decrease a few months after the end of treatments. Patients who receive bone marrow transplants may experience cancer-related fatigue for up to a year after treatment. 

So, while chronic fatigue after cancer treatment is challenging, it generally resolves with time.

Learn About Cancer Care Services at Baptist Health

Baptist Health provides world-class care for cancer patients. That includes using the most effective therapies available to treat their cancer and address cancer-related fatigue. If you’re feeling tired all the time due to cancer, your doctor can help.

Learn more about our cancer care services.