Dismiss Modal

Management

Fatigue and Cancer

Choose a preferred language

Fatigue is a feeling of being tired, weak, or exhausted. It's the most common side effect of cancer and cancer treatment. But fatigue does not mean the cancer is getting worse or that the cancer treatment isn't working. 

Some people with cancer have described fatigue as being tired to the bones or hitting a wall. Others say it's the most distressing side effect of cancer treatment. Cancer-related fatigue is different for everyone. It's important that the person who is experiencing it describes how they feel. Fatigue may make a person unable to work, do physical activity, be involved with family, socialize with friends, or carry out daily activities. Sometimes it even causes people to miss cancer treatments. 

If the person with cancer is easily distracted and unable to concentrate on mental work or activity, then they may have attentional fatigue. This is also called chemo brain. It's a common side effect of cancer treatment.

Depending on its cause, cancer-related fatigue can come and go or stay for a while. Fatigue from chemotherapy tends to be the worst a few days after treatment and then gets better before the next treatment. Fatigue from radiation usually starts slowly a few weeks after treatment starts. It often gets worse as treatment continues. It improves over time after treatment ends.


Causes of fatigue

We currently understand some of the causes of fatigue, but not all of them. Fatigue may be related to physical changes caused by cancer or its treatment. Cancer-related fatigue tends to be more severe than the fatigue people without cancer people sometimes have. This fatigue lasts longer and does not get better with sleep.

Low hemoglobin levels (anemia) is a common treatment side effect that's also related to fatigue. Hemoglobin carries oxygen in the blood. So if it is low, the body cells do not get as much oxygen as they need. People who are not well-nourished, don't drink enough fluid and are dehydrated, or are not able to move around much tend to have more fatigue. Uncontrolled pain, depression, and problems sleeping can also cause fatigue. Finally, the way a person handles stress, thinks, or behaves can influence fatigue. 

Featured in

© 2025 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.

Find a doctor that's right for you.

From routine check-ups to groundbreaking treatments and beyond, Crestner Health is here to help you live your healthiest life.

Search our doctors
Related Articles
Read article
Oncology
Coping with Advanced Cancer

Hearing that your cancer is incurable is shocking. It can be hard to know how to move forward.

Read article
Oncology
Coping with Cancer

You can find many ways to cope with stress. The goal of each approach, whether it is coping skills or relaxation methods, is to bring you from a place of tension to a place of serenity—mentally, physically, emotionally, and spiritually.

Read article
Oncology
Cancer Treatment and Low Platelet Count

effects. One possible side effect from cancer treatment is a low platelet count. This means the number of platelets in your blood is lower than normal. Read on to learn more.

Read article
Oncology
Nutrition During Chemotherapy

During chemotherapy, the energy provided by a healthy diet can help you rebuild normal cells. It can also help you keep up your strength and fight infection. These guidelines can help.