context: You're likely to have some fatigue while you're getting treated for breast cancer. That's one of the most common side effects of the disease and treatments for it. Fatigue isn't the same as being tired. Tiredness happens to everyone, and a good night's sleep usually re-energizes you. Fatigue is a daily lack of energy or whole-body tiredness that doesn't go away, even with good sleep. It can keep you from doing normal, daily things, and it affects your quality of life. Sometimes it's "acute," meaning it lasts a month or less. In other cases it's "chronic" and lasts up to 6 months or longer. Usually, it comes on suddenly, and may continue after you're done with your treatment. Here are some possible reasons for it, along with tips to help you get some of your energy back. The disease itself can be the problem. Tumor cells steal calories and nutrients from normal cells, and that leads to tiredness that won't seem to let up. Treatments can cause fatigue, too: Chemotherapy . Any chemo drug can cause you to have fatigue. It lasts for a few days in some people, while others say they have it throughout treatment or even afterward. Radiation can give you fatigue that tends to get worse over time. It usually lasts 3 to 4 weeks after your treatment stops, but it can continue for up to 3 months. Hormone therapy deprives the body of estrogen, and that can lead to fatigue that may last throughout your treatment or longer. Bone marrow transplant . This aggressive form of treatment can give you a daily lack of energy that lasts up to 1 year. Targeted therapy. High amounts of these medications can lead to long-lasting fatigue. Combination therapy. Getting more than one cancer treatment at the same time or one after the other also increases your chances of feeling listless. Surgery. Everyone recovers from surgery at different rates. This can also cause some daily exhaustion. Cancer treatments can cause anemia, a blood disorder where your body's cells don't get the oxygen they need. And side effects of treatments -- such as nausea, vomiting, mouth sores, taste changes, heartburn, or diarrhea -- can lower the amount of nutrition you get, which can make you feel worn-out. Medicines used to treat side effects like nausea, pain, depression, anxiety, and seizures can cause fatigue, too. So can hormonal changes related to medications. If your thyroid gland is underactive, your metabolism may slow down so much that your body doesn't burn food fast enough to give you energy. This is a common condition, but it can also happen after radiation therapy to the lymph nodes in the neck. In older people, being less active and having problems moving around can lead to fatigue. Younger people in treatment sometimes overexert themselves and bring on daily lack of energy or whole-body tiredness. Chronic, severe pain makes it worse. Stress doesn't help, either. Fatigue often happens when people try to keep their normal daily routines and activities during treatment. Changing your activities can help you save energy. Depression and fatigue often go hand in hand, but 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. Let your doctor know if you feel depressed all the time, were depressed before your cancer diagnosis, or are preoccupied with feelings of worthlessness. The first step is to try to figure out the source or sources of your fatigue. There may be more than one reason you're feeling this way. Your doctor can do tests to check for anemia or hypothyroidism. If you have one of these conditions, treatments can help. If you think your cancer treatment is the cause, you can talk to your doctor about ways to help you manage it, or discuss other options. Figure out your level of energy. Keep a diary for 1 week. Write down the times of day when you're most fatigued, and the times when you have the most energy. Note what you think might be the reasons why. Know the warning signs of fatigue: Tired eyes Tired legs Whole-body tiredness Stiff shoulders Trouble concentrating Weakness or malaise Boredom or lack of motivation Exhaustion, even after sleeping Irritability Nervousness, anxiety, or impatience 1. Plan ahead, and organize your work. Combine activities and simplify details. Ask family members or friends to help you with tasks when possible. 2. Pace yourself. A moderate pace is better than rushing through your day. 3. Balance periods of rest and work. Use your energy only on important tasks. Schedule rest before you become fatigued -- frequent, short breaks are helpful. 4. Alternate sitting and standing. When you sit, use a chair with good back support. Sit up with your back straight and your shoulders back. 5. Try to work without bending over. Adjust the level of your work instead. When you have to lift something, bend your knees and use your leg muscles to lift, not your back. 6. Limit work that requires reaching over your head or that adds to muscle tension. Change where you store items to reduce trips or reaching. Rather than moving a large load, break it into smaller ones, or use a cart. 7. Breathe evenly, and wear comfortable clothes to allow for free and easy breathing. 8. Avoid too-hot or too-cold temperatures. Don't take long, hot showers or baths. Cancer-related fatigue can get worse if you're not eating enough or if you're not eating the right foods. A balanced diet can help you feel better and have more energy. Here are some ways to improve your diet: Get enough calories. If you have cancer, you need about 15 calories per pound of weight if your weight has been stable. Add 500 calories per day if you've lost weight. For example, a person who weighs 150 pounds needs about 2,250 calories per day to maintain his or her weight. Get plenty of protein. It rebuilds and repairs damaged cells. Women need about 46 grams per day, and men need 56 grams. Good sources of protein include dairy foods, meat, eggs, and beans. Drink plenty of fluids. That will help you avoid fatigue that comes from dehydration. And it'll help you get calories. Drink things like water, juice, milk, broth, and milkshakes. Avoid drinks with caffeine. Also, you'll need more fluids if you have vomiting or diarrhea. Get enough vitamins. Ask your doctor whether you should take a vitamin supplement if you're not sure you're getting enough nutrients. A multivitamin provides many of the nutrients your body needs. But vitamin supplements don't have calories, so make sure you eat nutritious foods to get your calories. Consider seeing a registered dietitian. They can help you with any eating problems that may be keeping you from getting proper nutrition (such as problems swallowing, changes in tastes, or feeling full quickly). A dietitian can also suggest ways to get more calories and protein in smaller amounts of food. Your cancer and treatments may make you feel drained, leaving you lying in bed or sitting in chairs for hours. But that sort of inactivity can lead to feelings of anxiety, depression, weakness, and further fatigue. Regular, moderate exercise can ease those feelings, help you stay active, and give you more energy. Even during your cancer treatment, you may be able to keep exercising. Here are some tips: Check with your doctor before you begin an exercise program. Start slowly if you get the OK. Give your body time to adjust. Keep a regular exercise schedule. Try to be active at least 150 minutes a week. If you're just starting, build up to this amount over time. The right kind of exercise never makes you feel sore, stiff, or exhausted. If you that happens or you feel out of breath, you're overdoing it. Swimming, brisk walking, stationary cycling, and low-impact aerobics (taught by a certified instructor) might be good choices. But talk to your doctor if you have any questions about exercises that are safe for you. Managing stress can play an important role in fighting 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 toward easing 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 support groups can be a source of strength, too. Other people with the disease may understand what you're going through. Relaxation techniques like deep breathing or visualization can lower stress, too. Or just do low-key things that are fun for you -- read, listen to music, or knit, for example. Let your doctor know if your stress seems out of control. He can help you feel better. Although cancer-related fatigue is a common side effect of cancer and its treatments, you should mention any of your concerns to your doctor. There are times when fatigue may be a clue to an underlying medical problem. Other times, there may be things your doctor can do to help control fatigue. Be sure to let your doctor or nurse know if you have: Shortness of breath Pain Side effects from treatments (such as nausea, vomiting, diarrhea, or loss of appetite) Anxiety or nervousness Depression