The exact causes of cancer fatigue and how best to treat it aren't always clear. Find out what doctors know about cancer fatigue and what you can do about it. By Mayo Clinic Staff

Fatigue, usually described as feeling tired, weak or exhausted, affects most people during cancer treatment. Cancer fatigue can result from the side effects of treatment or the cancer itself.

Cancer fatigue may be caused by many factors, and the factors that contribute to your cancer fatigue may be completely different from those of someone you know. However, possible contributing factors include:

  • Your cancer. Your cancer can cause changes to your body that can lead to fatigue. For instance, some cancers release proteins called cytokines, which are thought to cause fatigue. Other cancers can increase your body's need for energy, weaken your muscles or alter your body's hormones, all of which may contribute to fatigue.
  • Cancer treatment. Chemotherapy, radiation therapy, surgery, bone marrow transplantation and biological therapy may all cause fatigue. You may experience fatigue when chemotherapy or radiation therapy destroys healthy cells in addition to the targeted cancer cells. Fatigue may occur as your body tries to repair the damage to healthy cells and tissue. Some treatment side effects — such as anemia, nausea, vomiting, pain, insomnia and changes in mood — also may cause fatigue.
  • Anemia. You might develop anemia if your treatment destroys too many healthy red blood cells. You can also develop anemia if the cancer has spread to your bone marrow and interferes with blood cell production or causes you to lose blood.
  • Pain. If you experience chronic pain, you may be less active, eat less, sleep less and become depressed, all of which may add to your fatigue.
  • Emotions. Anxiety, stress or depression associated with your cancer diagnosis also may lead to fatigue.
  • Lack of sleep. If you're sleeping less at night or if your sleep is frequently interrupted, you may experience fatigue.
  • Poor nutrition. In order to work efficiently, you need the energy that a healthy diet provides. When you have cancer, changes can occur in your need for and ability to process nutrients. These changes can lead to poor nutrition, resulting in fatigue. For example, you may need more nutrients than usual or you may not be able to process nutrients adequately. You may also take in fewer nutrients if your appetite wanes or if treatment side effects, such as nausea and vomiting, make it difficult to eat.
  • Medications. Certain medications, such as pain relievers, can cause fatigue.
  • Lack of exercise. If you're used to being on the go, slowing down can make you feel fatigued. Though you will have good days and bad days, try to maintain your normal level of activity if you can.
  • Hormonal changes. Many hormonal changes can occur during cancer treatment. Hormonal therapies may modify hormones as a way to treat cancer. Hormonal changes also may occur as side effects of treatments, such as surgery, radiation therapy or chemotherapy. Changes to the thyroid gland, adrenal glands, testes or ovaries can all cause fatigue.

Not everyone who has cancer experiences fatigue. And if you do, the level of cancer fatigue you experience can vary — you may feel a mild lack of energy, or you may feel completely wiped out. Your cancer fatigue may occur episodically and last just a short while, or it may last for several months after you complete treatment.

Some fatigue during cancer treatment is to be expected. But if you find that cancer fatigue is persistent, lasting weeks, and interferes with your ability to go about your everyday tasks, tell your doctor.

Tell your doctor right away if you experience:

  • Confusion
  • Dizziness
  • Loss of balance
  • Inability to get out of bed for more than 24 hours
  • Severe shortness of breath
  • Worsening signs and symptoms

If you're fatigued, your doctor may examine you and ask you questions to assess the severity and nature of your symptoms. This gives your doctor clues about what's causing your cancer fatigue and how to treat it.

Your doctor might ask questions such as these:

  • When did you begin experiencing fatigue?
  • Has it progressed since your diagnosis?
  • How severe is it?
  • How long does it last?
  • What eases it?
  • What makes it worse?
  • How does it affect your daily life?
  • Do you experience shortness of breath or chest discomfort?
  • How well are you sleeping?
  • How and what are you eating?
  • How are you feeling emotionally?

In addition to these questions, your doctor will likely conduct a physical exam and further evaluate your medical history, the type or types of treatment you are receiving or have received, and any medications you're taking. He or she may recommend some tests, such as blood tests or X-rays, specific to your condition.

Because cancer-related fatigue may be caused by many factors, your doctor may suggest more than one method to reduce and cope with your symptoms. These may include self-care methods and, in certain cases, medications or medical procedures.

Medical interventions
Medications may be available to treat the underlying cause of your fatigue. For instance, if your fatigue is the result of anemia, blood transfusions may help. Medications that stimulate your bone marrow to produce more red blood cells might be another option, though, as with any medicine, these medications must be used with appropriate cautions.

If you're depressed, your doctor might suggest medications that can help reduce fatigue, increase appetite and improve your sense of well-being.

Self-care options
Coping with fatigue might require things you can do on your own. You might try to:

  • Take it easy. Set aside time in your day to rest. Take short naps — no longer than an hour — throughout the day rather than resting for one long period.
  • Conserve your energy. Save your energy for your most important activities. Keep track of the times when you feel your best, and plan to do your important activities during those times. Ask for help when needed.
  • Maintain your energy. Drinking lots of fluids and eating well can help keep your energy reserves up. Limit or avoid caffeine and alcohol. If nausea and vomiting make it hard to eat, talk to your doctor about these side effects.
  • Get moving. When you feel up to it, light exercise throughout the week may help you preserve your energy level. But keep in mind that once you start feeling fatigued, it may be too late to start an exercise program because it's hard to find the energy to get going. Instead, exercise regularly as you start treatment. You'll get in the routine of exercising, and it may even help you prevent fatigue during treatment.

Don't assume the fatigue you're experiencing is just part of the cancer experience. If it's frustrating you or affecting your ability to go about your day, it's time to talk with your doctor.

Though fatigue is a common symptom when you have cancer, there are steps you can take to reduce or cope with your condition. If you're feeling fatigued, talk with your doctor about what factors might be causing your fatigue and what you can do to improve them.

Jul. 28, 2011