Cancer Fatigue
After being diagnosed with cancer, you may feel tired, weak, listless, exhausted — basically like you have no energy. Sleep and rest don’t help. Your arms and legs may feel heavy and sluggish. You may have little desire to do anything and find it too tiring to eat or even walk to the door, let alone go to work or school. This is cancer fatigue.
Also called cancer-related fatigue by doctors, cancer fatigue is the most common side effect of cancer treatment. A 2023 study found that more than 70% of people diagnosed with cancer report having fatigue.
Cancer fatigue can dramatically affect your quality of life by making you feel too exhausted to participate in your usual activities. In many cases, physical fatigue can lead to mental fatigue and mood changes. But the good news is there are ways to ease fatigue, including exercise and diet changes.
Did you know that exercise can help with many breast cancer treatment side effects? Our video series, Exercises to Relieve Side Effects, is designed especially for people living with breast cancer — no matter your fitness or energy level.
Watch the Exercises to Help With Fatigue video.
What causes cancer fatigue?
There are a number of things that can cause cancer fatigue.
Being diagnosed with breast cancer: Breast cancer causes changes in your body that can lead to fatigue. Many breast cancers release proteins called cytokines, which have been linked to fatigue. Breast cancer also may change your body’s hormone levels and cause inflammation, both of which may contribute to fatigue.
Breast cancer treatment: Surgery, radiation therapy, chemotherapy, hormonal therapy, targeted therapy, and immunotherapy all may cause fatigue. Many medicines used to treat breast cancer affect both healthy cells and cancer cells. You may feel fatigue as your body works to repair or replace damaged healthy cells.
Treatment side effects: A number of side effects are also linked to fatigue, including pain, nausea, low red blood cell counts (anemia), low white blood cell counts, diarrhea, dehydration, trouble sleeping, and vomiting. These side effects can cause fatigue or make it more severe.
Your emotional health: People diagnosed with breast cancer often report feeling stressed, anxious, or depressed. All these emotions can lead to fatigue.
Poor nutrition: If you’ve been diagnosed with breast cancer, you may need more or different nutrients than usual. But it can be hard to stick to a healthy diet and eat enough if treatment makes you feel sick or throw up.
Pain medicines: A number of pain medicines, such as codeine, oxycodone, and morphine, are known to cause fatigue.
Lack of exercise. It may sound counterintuitive, but exercising, even gentle walking, can give you more energy. Not exercising can make you feel sluggish and tired.
Cancer fatigue symptoms
People describe cancer fatigue in many different ways. Common symptoms include:
feeling a lack of energy
sleeping less
sleeping more, but still feeling tired
having no interest in your normal activities
having trouble thinking or concentrating
feeling sad or cranky
paying less attention to your personal appearance
feeling so tired you can’t do even small tasks, like use the television remote or make a phone call
feeling very weak
How long does cancer fatigue last?
Unfortunately, if you have cancer fatigue, there is no way to know how long it might last or how severe it might be. Fatigue from breast cancer and breast cancer treatment can start before, during, or after treatment and last for weeks, months, or even years after you finish treatment.
It’s important to know that the effects of cancer fatigue can change from day to day. If you’re receiving chemotherapy, targeted therapy, or immunotherapy in cycles, the fatigue is often worse at the beginning of the cycle and then eases until the next cycle starts. If you’re receiving radiation therapy, fatigue usually gets worse as treatment goes on and then eases a few weeks or months after you finish treatment.
Managing cancer fatigue
If you think you have cancer fatigue, the first thing to do is to talk with your doctor. Many people think that fatigue is just part of cancer treatment, so they don’t mention it. Although fatigue is common, it can be treated and managed.
Usually, there is no single cause of cancer fatigue. So your doctor may add other clinicians to your care team, including palliative care professionals, nurses, social workers, physical therapists, pharmacists, cancer exercise trainers, and registered dietitians to help you manage fatigue.
It can help your care team develop strategies to ease fatigue if you keep a journal or log that includes:
all your breast cancer-related symptoms and treatment side effects
when each symptom and side effect started
how severe the symptoms and side effects are throughout each day
how you’re feeling physically and emotionally each day
Treating specific side effects, such as pain or anemia, can help ease cancer fatigue, but your doctor is likely to recommend other steps and therapies that can help manage fatigue.
Research suggests that a healthy diet full of whole grains, fruits and vegetables (especially broccoli, berries, spinach, and carrots) fish, nuts and seeds, and plant oils, such as flaxseed oil, can help ease fatigue.
It’s also important to drink enough water. Being dehydrated can contribute to fatigue. Your doctor also may recommend that you avoid caffeine because it can dehydrate you and disrupt your sleep.
If you’re unsure about how to eat a healthy, balanced diet, ask your doctor for a referral to a registered dietitian who has experience working with people with cancer. You also can visit the Academy of Nutrition and Dietetics to search for a nutrition expert.
A number of therapies have been shown to ease stress and anxiety, which can help with fatigue. Mindfulness meditation, counseling, acupuncture, journaling, yoga, massage therapy, and cognitive behavioral therapy can either lower stress or help ease fatigue.
If you’re worrying about meeting all your daily obligations — cleaning, child care, shopping, or yard work, for example — ask family and friends if they can help. Many loved ones want to help people who are dealing with cancer treatment but aren’t sure what to do. Telling them what you need can help both you and your family.
Many experts recommend trying to sleep seven to eight hours each night, aiming to go to bed and wake up at the same time each day, to help with fatigue.
The Sleep Foundation recommends developing a series of activities you do every night in the hour or half hour before you go to bed. This creates habits that tell your brain it’s time to get ready to sleep. Your routine could include logging off all electronics, reading a book, meditating, having a small mug of herbal tea, or listening to relaxing music.
If you get tired during the day, take only short naps – don’t sleep for more than 30 minutes. If you nap longer, you may have trouble sleeping at night.
Cancer fatigue and exercise
Exercise is so important for managing fatigue that the American Society of Clinical Oncology (ASCO) 2024 guidelines for managing fatigue list exercise as the first recommendation. The ASCO experts said the recommendation was based on a large number of studies consistently showing that exercise can help ease cancer fatigue.
The experts said that combining aerobic and strength exercises, as well as strength exercises alone, consistently helped ease fatigue.
In the video below, Sami Mansfield, a certified cancer trainer and founder of Cancer Wellness for Life, provides easy-to-follow instructions for exercises that can help reduce fatigue. The short full-body workout includes resistance exercises that you can easily modify as you need.
— Last updated on March 1, 2025 at 4:56 PM
