What Is Cancer-related Fatigue?

The fatigue that comes with cancer, called cancer-related fatigue, is different from the fatigue of daily life. Cancer-related fatigue is not the tired feeling people remember having before they had cancer.

People describe it as feeling weak, listless, drained, or “washed out.” Some may feel too tired to eat, walk to the bathroom, or even use the TV remote. It can be hard to think or move. Rest does not make it go away, and just a little activity can be exhausting. For some people, this kind of fatigue causes more distress than pain, nausea, vomiting, or depression.

Here are some signs of cancer-related fatigue that you and your family can watch for.

  • You feel tired and it doesn’t get better with rest or sleep, it keeps coming back, or it becomes severe.
  • You’re more tired than usual during or after an activity.
  • You’re feeling tired and it’s not related to an activity.
  • You’re too tired to do the things you normally do.
  • Your arms and legs feel heavy and hard to move.
  • You have no energy.
  • You feel weak.
  • You spend more time in bed and/or sleep more. Or, you may have trouble sleeping.
  • You stay in bed for more than 24 hours.
  • You become confused or can’t concentrate or focus your thoughts.
  • Your tiredness disrupts your work, social life, or daily routine.

It may be hard for you to talk about it, but tell your cancer care team about your fatigue. Tell them how it’s affecting your life. Someone on your team should be able to help you if they know you’re having this problem. Managing fatigue is part of good cancer care. Work with your cancer care team to find and treat the causes of your fatigue.

How long does cancer related fatigue last?

Cancer-related fatigue can last from months to years. It often continues after treatment ends.

  • For people getting chemotherapy in cycles, fatigue often gets worse in the first few days and then gets better until the next treatment, when the pattern starts again.
  • For those getting radiation, fatigue usually gets worse as the treatment goes on.

Cancer-related fatigue can:

  • Differ from one day to the next in how bad it is and how much it bothers you
  • Be overwhelming and make it hard for you to feel well
  • Make it hard for you to be with your friends and family
  • Make it hard for you to do things you normally do, including going to work
  • Make it harder for you to follow your cancer treatment plan

What causes cancer-related fatigue?

The causes of cancer-related fatigue are not fully understood. It may be the cancer and/or the cancer treatment. Here are some possible causes:

  • Cancer and cancer treatment can change normal protein and hormone levels that are linked to inflammatory processes which can cause or worsen fatigue.
  • Treatments kill normal cells and cancer cells, which leads to a build-up of cell waste. Your body uses extra energy to clean up and repair damaged tissue.
  • Cancer forms toxic substances in the body that change the way normal cells work.

Fatigue is often caused by more than one thing. Some of the more common causes of cancer-related fatigue are:


There are many different causes of anemia. Cancer itself can cause fatigue by spreading to the bone marrow and causing a low red blood cell count (anemia). Red blood cells carry oxygen to fuel all the cells in the body. Too few red blood cells mean not enough energy to meet the body’s needs. Chemo and radiation can also affect the bone marrow and blood cells counts.

For more on this, see Anemia in People With Cancer.


Cancer pain can make you less active, make you not want to eat, cause sleep problems, and cause depression – all of which can lead to fatigue. Pain should not be accepted as part of cancer treatment. Something can always be done to make pain better. Talk to your doctor or nurse to get more information about treating cancer pain.

Emotional distress

People with cancer go through a lot of different, unpleasant emotions. These uncomfortable feelings are often called distress. Distress can include a feeling of sadness about the loss of good health or fear of what will happen in the future. It’s normal to have these feelings. But sometimes the distress becomes so great that it causes physical problems like fatigue. Depression and anxiety are common types of distress that can cause or worsen fatigue.

Sleep problems

If you wake up often during the night, have trouble falling asleep, or wake up early in the morning and can’t go back to sleep, you’re probably not getting the rest you need. These sleep changes can lead to fatigue.


Many medicines can cause fatigue and problems with thinking. This includes certain over-the-counter drugs and possibly herbs and other supplements, as well as prescription medicines. The drugs most likely to cause fatigue are:

  • Pain medicines
  • Sleep medicines
  • Anti-depressants
  • Anti-nausea medicines
  • Anti-seizure medicines
  • Certain antihistamines
  • Certain heart medicines

Some of these drugs can also make you feel sleepy. The degree of sleepiness varies from person to person. Taking many drugs that have a lot of side effects can make fatigue worse, too. It’s important to tell your team about all vitamins, herbs, supplements, and medicines you take. Don’t forget to tell them about the non-prescription drugs and those you use every now and then as needed.

Keeping track of everything you take, along with the doses, times, and when you have symptoms, might help you figure out which ones may be part of your fatigue.

Other health problems

Many people have other medical problems or illnesses that aren’t related to cancer but may add to fatigue. Examples of other medical problems that could be part of fatigue are:

  • Problems with other organs, such as the heart, lungs, liver, kidneys, or brain
  • Nervous system problems
  • Digestive system problems
  • Infections, such as pneumonia, urinary tract infections, or viral illnesses
  • Dehydration
  • Low adrenal gland function (rare, but can cause low blood pressure, fainting, and dehydration)
  • Low sex hormones (such as estrogen in women or testosterone in men)
  • Low thyroid function

If needed, your doctor can test you to find out if any of these are making your fatigue worse. For example, low thyroid gland function is fairly common in people in the United States. It can often be detected by a simple blood test and is easy to treat.

Poor nutrition

Your body needs protein, carbohydrates, fats, vitamins, minerals, and water to do its work. Fatigue can be caused by poor intake of food, fluids, and certain minerals as well as the following:

  • Changes in metabolism (the body’s ability to break down and use food)
  • The increased energy needed to repair damaged cells
  • Uncontrolled tumor growth competing for nutrients (the cancer takes energy, protein, vitamins, and the like, for its own growth)
  • Poor appetite (you don’t feel like eating)
  • Nausea and vomiting
  • Diarrhea

Your doctor may order tests to measure your blood levels of important minerals, like sodium, potassium, calcium, and magnesium. You can ask to see a registered dietitian who can help you learn how to best meet your nutrition needs during this time.

You can find more information in Nutrition for People With Cancer.

Lack of exercise

Cancer treatment along with less physical activity can make you less able to do the things you used to do. You might find that it takes much more effort and more energy to do the things you need to do.

Though it may seem strange, physical activity can help decrease fatigue and help build up your stamina to do more of your usual activities. Resting, on the other hand, can make fatigue worse in the long run.

Talk to your cancer care team before you start any exercise program. A careful work-up by a physical therapist can help you plan the right physical activities for you.

Alcohol or other non-prescribed drugs

Alcohol and other “recreational” drugs might make you feel better for a short time, but in the long run they can make you feel more tired and disrupt your sleep. They can also interact with the cancer drugs you are taking and may cause their own medical problems.

If you think drinking or other drugs might be a problem for you, talk honestly with your doctor about how much and how often you drink or use drugs. Keep in mind, too, that alcohol is a carcinogen (cancer-causing agent), which many people with cancer prefer to completely avoid.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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National Cancer Institute. Fatigue PDQ (Health Professional Version). 8/28/14. Accessed at www.cancer.gov/about-cancer/treatment/side-effects/fatigue/fatigue-hp-pdq on May 2, 2016.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology. Cancer-Related Fatigue – V.1.2016. Accessed at www.nccn.org/professionals/physician_gls/f_guidelines.asp on May 2, 2016.

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Last Medical Review: October 22, 2018 Last Revised: October 22, 2018

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