Cancer Fatigue: Why It Happens and What Helps

Cancer fatigue is a condition caused by cancer or cancer treatment in which you feel exhausted or extremely tired. Some people feel extreme fatigue most of the time and are unable to carry out day-to-day tasks. Others feel only very tired. It may also be called cancer-related fatigue.

Cancer fatigue is different from ordinary tiredness. When a healthy person is tired, fatigue is usually caused by activity and goes away after resting or sleeping. Cancer fatigue is not completely relieved by sleep or rest, and it may happen after little or no activity.

Signs of cancer fatigue include having no energy, feeling drained or heavy, having trouble thinking or remembering, feeling physically and emotionally exhausted, and not feeling rested even after sleeping.

Fatigue is one of the most common side effects of cancer treatment. More than 80% of people with cancer experience fatigue while receiving chemotherapy or radiation therapy.

Fatigue can begin before, during, or after treatment. Sometimes it's an early symptom of cancer, or it can come from the stress of a diagnosis. It may worsen gradually or come on suddenly. Fatigue usually decreases after treatment ends, but some people still feel it for months or years.

Cancer itself, cancer treatments, and the side effects of treatment can all cause fatigue.

• The cancer itself. Cancer cells use calories and nutrients your body needs for energy. Cancer can also raise levels of cytokines—natural substances that help fight infection but can cause fatigue at high levels. Blood cancers, and cancers that affect hormones or digestion, are more likely to cause fatigue.
• Treatments. Surgery, chemotherapy, radiation therapy, hormone therapy, immunotherapy, and targeted therapy can all lower your energy. Receiving more than one treatment can increase fatigue.
• Other side effects. Anemia, appetite loss, diarrhea, hot flashes, infection, pain, sleep problems, and vomiting can all cause or worsen fatigue.
• The emotional impact of cancer. Anxiety, worry, and high distress can lead to physical problems including fatigue, insomnia, and appetite loss.

Tell your health care team if you feel very weak and tired—especially if you can't do your normal activities or are still very tired even after resting.

Your doctor may give you a chart, log, or fatigue diary to record your energy level each day. Along with a physical exam and blood tests (to check for anemia or infection), this helps your team find the best way to manage your fatigue.

Your team often treats fatigue by relieving related conditions, such as anemia, pain, or depression. When the cause isn't known, they treat the symptoms and teach you ways to cope.

Things that may help lessen or manage fatigue include:

• Rest and sleep. Practice good sleep habits, plan short naps of less than an hour during the day, and start with what's most important when your energy is highest.
• Exercise and physical activity. Exercise, including walking, may help you feel better and have more energy during and after treatment. Choose an activity you enjoy and make a plan with your team.
• Food and drink. A registered dietitian can help you get the nutrients you need for energy. Many people find small, frequent meals easier than three big ones. Drink plenty of water and limit caffeine and alcohol.
• Mind–body practices. Qigong, tai chi, and yoga have been found to reduce fatigue for people with cancer. Relaxation techniques, guided imagery, and acupuncture may also help.

There are no standard drugs approved just for cancer fatigue, though several are being studied.

• Call 911 or go to an emergency department if you pass out, or come close to it, when you stand up or walk across a room.
• Call your care team the same day if the tiredness arrives with breathlessness, a racing heartbeat, light-headedness, or skin that has gone pale. NCI lists those as signs of anemia, which is treatable once it is found.
• Call your care team the same day if exhaustion appears suddenly over a day or two rather than building slowly.
• Do not wait at all if exhaustion comes with a temperature of 100.4°F (38°C) or higher, or with shaking chills, while you are having treatment. The CDC treats a fever during cancer treatment as an emergency, so use the urgent number your team gave you or head for an emergency department.
• Call your care team within a day or two if you are too weak to manage your normal activities, or you are still worn out after resting and sleeping. NCI asks you to report exactly that.
• Call your care team within a day or two if low energy is dragging your mood down, or you are skipping meals and fluids because moving feels like too much.

Source for the anemia signs: National Cancer Institute — Anemia and Cancer Treatment. Source for the fever advice: CDC — Fever and Cancer Treatment.

You are not alone. Family and friends can help with tasks like making meals, cleaning, and driving. Your nurse or social worker may help you find services for personal needs such as eating and bathing. And if you are caring for someone with fatigue, support and resources are available to you too.