Fatigue is a feeling of being physically, emotionally, or mentally tired, weak, or exhausted. It's a symptom of cancer and also the most common side effect of cancer treatment. Cancer-related fatigue tends to be more severe than the fatigue people without cancer sometimes have. Cancer-related fatigue lasts longer and is not relieved by sleep.

Some people with cancer have described fatigue as being tired to the bones or hitting a wall. Others say it is the most distressing side effect of cancer treatment. Fatigue may make you unable to work or do physical activity. It can make it hard to be involved with your family, socialize with friends, or complete daily activities. It can also make it hard for you to focus and pay attention. Sometimes it even causes people to miss cancer treatments.

Having fatigue doesn't mean the cancer is getting worse or treatment isn't working. Fatigue can come and go, or it might 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 can start slowly after a few weeks of treatment and get worse as treatment goes on. It may last many months after treatment is finished.

Fatigue is different for everyone. It's important to talk about it with your health care team and describe how you feel. Some of the problems linked to cancer-related fatigue can be treated.

Some of the causes of fatigue are understood, but not all of them. Fatigue may be caused by:

• Physical changes caused by cancer.
• Cancer treatment (chemotherapy, radiation, surgery, hormone therapy, immunotherapy, or bone marrow transplant).
• Anemia (low level of red blood cells).
• Medicines.
• Changes in hormone levels.
• Infection.
• Pain.
• Stress.
• Lack of sleep.
• Not eating enough calories.
• Dehydration.
• Not being active.
• Trouble breathing or low oxygen.
• Anxiety or depression.

Other things that can make fatigue worse may be harder to treat, like financial worries and fears or concerns related to cancer or its treatment. It's important to talk about these things. There are people who can help, like a social worker or counselor. Talking about fears or problems can help you feel more in control and might lead you to solutions to the problems. A support group can also be very helpful. A group can give you ongoing support and a place to share creative solutions to problems with fatigue. Talk with your doctor for more information.

The treatment will depend on your symptoms and the cause of your fatigue. Anemia may be treated with dietary changes, a blood transfusion, or medicines. If a medicine is causing your fatigue, your doctor may change the dose or type of medicine. You may see a dietitian to discuss nutrition and eating strategies to improve your energy. Fatigue may be treated with the lifestyle changes discussed below.

Cancer-related fatigue can change from day to day. It's important to learn ways to conserve energy. It helps to think of energy like money. You have only a limited amount of it. How do you want to spend it? What activities are most important? What helps restore energy?

To manage cancer-related fatigue or help lessen it, try to:

• Save your energy for activities that are important to you.
• Eat a well-balanced diet that is high in protein, calories, fruits, and vegetables. Talk with your doctor about taking a daily multivitamin.
• Drink plenty of fluids.
• Regularly do gentle exercise. Even a short walk can help. Talk with your doctor about the type of exercise that's best for you right now.
• Talk about problems with friends and family or the health care team.
• Ask for help with chores or tasks.
• Take short naps or rest breaks that are 30 minutes or less. Longer rest periods can make it difficult to sleep at night.
• Try to go to bed at the same time every night and aim for 7 to 8 hours of sleep.
• Stay away from caffeine.
• Don't exercise in the evening or close to bedtime.

The most important thing you can do is talk with your health care team about fatigue and how it's affecting your daily life. Only you can describe your fatigue. It might help to talk about these things:

• When the fatigue started
• How long it lasts
• What makes it better or worse
• How well you're sleeping
• What things you can't do because of fatigue
• If you have pain, trouble breathing, nausea, or other problems that may be linked to sleep problems and fatigue
• If the medicines you're taking might cause fatigue

Be sure to talk with your doctor about how you can manage or lessen fatigue.