context: Fatigue is often confused with tiredness. Tiredness happens to everyone -- it's a feeling you expect after certain activities or at the end of the day. Usually, you know why you are tired and a good night's sleep solves the problem. Fatigue is a daily lack of energy; it is excessive whole-body tiredness not relieved by sleep. It can last for a short time (a month or less) or stay around for longer (six months or longer). Fatigue can prevent you from functioning normally and gets in the way of things you enjoy or need to do. Cancer-related fatigue is one of the most common side effects of cancer and its treatment. It is not predictable by tumor type, treatment, or stage of illness. Usually, it comes on suddenly, does not result from activity or exertion, and is not relieved by rest or sleep. It is often described as "paralyzing" and may continue even after treatment is complete. The exact reason for cancer-related fatigue is unknown. It may be related to the disease itself or its treatments. The following cancer treatments are commonly associated with fatigue: Chemotherapy . Any chemotherapy drug may cause fatigue. Fatigue usually develops after several weeks of chemotherapy. In some, fatigue lasts a few days, while others say the problem persists throughout the course of treatment and even after the treatment is complete. Radiation therapy . Radiation can cause fatigue that increases over time. This can occur regardless of the treatment site. Fatigue usually lasts from three to four weeks after treatment stops, but can continue for up to two to three months. Combination therapy. More than one cancer treatment at the same time or one after the other increases the chances of developing fatigue. Bone marrow transplant . This aggressive form of treatment can cause fatigue that lasts up to one year. Biologic therapy . Biologics can also cause fatigue. Cancer cells compete for nutrients, often at the expense of the normal cells' growth. In addition to fatigue, weight loss and decreased appetite are common. Decreased nutrition from the side effects of treatments (such as nausea, vomiting, mouth sores, taste changes, heartburn, or diarrhea) can cause fatigue. Cancer treatments, specifically chemotherapy, can decrease the number of red blood cells, causing anemia. Red blood cells deliver oxygen throughout the body, so when tissues don't get enough oxygen, you can feel fatigue. Some drugs used to treat side effects such as nausea, pain, depression, anxiety, and seizures can cause fatigue. Research shows that pain also plays a role in fatigue. Stress can worsen feelings of fatigue. Stress can result from dealing with the disease and the "unknowns," as well as from worrying about daily accomplishments or trying to meet the expectations of others. Depression and fatigue often go hand-in-hand. It may not be clear which started first. One way to sort this out is to try to understand your depressed feelings and how they affect your life. If you are depressed all the time, were depressed before your cancer diagnosis, are preoccupied with feeling worthless and useless, you may need treatment for depression. The best way to combat fatigue is to treat the underlying medical cause. Unfortunately, the exact cause is often unknown, or there may be multiple causes. Causes of fatigue must be managed on an individual basis. For example, there are treatments that may improve fatigue caused by an under-active thyroid or anemia. The following guidelines may help you combat fatigue. Keep a diary for one week to identify the time of day when you are either most fatigued or have the most energy. Note what you think may be contributing factors. Be alert to your personal warning signs of fatigue. Signs may include whole-body tiredness unrelieved by sleep, decreased energy or a lack of energy, mental and emotional exhaustion, inability to concentrate, weakness, or malaise. There are several ways to combat fatigue by conserving your energy. Here are some suggestions: Plan ahead and organize your work Change storage of items to reduce trips and make them easier to reach. Prioritize activities and delegate tasks when needed. Combine activities and simplify details. Schedule rest Balance periods of rest and work. Rest before you become fatigued -- frequent, short rests are beneficial. Pace yourself A moderate pace is better than rushing through activities. Reduce sudden or prolonged strains. Alternate sitting and standing. Carry several small loads instead of one large one, or use a cart. Address Other Medical Problems Treating medical problems and symptoms that cause fatigue can also help. Examples include anemia, sleep problems, pain, depression, underactive thyroid, and dehydration. Cancer-related fatigue is often made worse if you are not eating or drinking enough or if you are not eating the right foods. Maintaining good nutrition can help you feel better and have more energy. Make an appointment with a dietitian. A registered dietitian provides suggestions to work around any eating problems that may be interfering with proper nutrition (such as early feeling of fullness, swallowing difficulty, or taste changes). A dietitian can also suggest ways to maximize calories and include proteins in smaller amounts of food (such as powdered milk, instant breakfast drinks, and other commercial supplements or food additives). Decreased physical activity, which may be the result of cancer or treatment, can contribute to tiredness and lack of energy. Scientists have found that even healthy athletes forced to spend extended periods in bed or sitting in chairs develop feelings of anxiety, depression, and fatigue. Regular, moderate exercise can decrease these feelings, help you stay active and increase your energy. Even during cancer therapy, it is often possible to continue exercising. In fact, research has shown that cancer patients who perform a moderate exercise routine have a better quality of life and may have better outcomes. Here are some exercise guidelines to keep in mind if you have cancer: Check with your doctor before beginning an exercise program. A physical therapist can be helpful in planning a program for you. A good exercise program starts slowly, allowing your body time to adjust. Keep a regular exercise schedule. The right kind of exercise never makes you feel sore, stiff, or exhausted. If you experience soreness, stiffness, exhaustion, or feel out of breath as a result of your exercise, you are overdoing it. Most exercises are safe, as long as you exercise with caution and don't overdo it. Among the safest and most productive activities are swimming, brisk walking, indoor stationary cycling, and low-impact aerobics (taught by a certified instructor). These activities carry little risk of injury and benefit your entire body. Managing stress can play an important role in combating cancer-related fatigue. Here are some suggestions that may help. Adjust your expectations. For example, if you have a list of 10 things you want to accomplish today, pare it down to two and leave the rest for other days. A sense of accomplishment goes a long way to reducing stress. Help others understand and support you. Family and friends can be helpful if they can "put themselves in your shoes" and understand what fatigue means to you. Cancer groups can be a source of support, as well. Other people with cancer understand what you are going through. Relaxation techniques such as audiotapes that teach deep breathing or visualization can help reduce stress. Activities that divert your attention away from fatigue can also be helpful. For example, activities such as knitting, reading, or listening to music require little physical energy but require attention. If your stress seems out of control, talk to a health care professional. Although cancer-related fatigue is a common, and often expected, side effect of cancer and its treatments, you should feel free to mention your concerns to your doctors. There are times when fatigue may be a clue to an underlying medical problem. Other times, there may be treatments to help control some of the causes of fatigue. Finally, there may be suggestions that are more specific to your situation that would help in combating your fatigue. Be sure to let your doctor or nurse know if you have: Increased shortness of breath with minimal exertion Uncontrolled pain Inability to control side effects from treatments (such as nausea, vomiting, diarrhea, or loss of appetite) Uncontrollable anxiety or nervousness Ongoing depression