Side Effects From Breast Cancer Treatments

Medically Reviewed by Hansa D. Bhargava, MD on January 28, 2021

Chemotherapy and radiation destroy breast cancer cells. But these treatments can also affect healthy cells and can change how you feel. They might cause:

Medications and other therapies can help ease many of these side effects.

Loss of Appetite

Breast cancer treatment may make you feel not hungry, which can make it hard to get the nutrition you need. Try these tips to make sure you’re eating a healthy diet:

  • Eat a few small meals during the day instead of three large ones.
  • Try an "instant breakfast" mix or other nutritional shakes between meals.
  • Eat your largest meal of the day when you are most hungry.
  • Drink water or other beverages either a half hour before or after meals so they don’t make you too full.
  • Try moderate exercise to increase your appetite, as long as your doctor says it’s OK.

Nausea and Vomiting

Some -- but not all -- people getting cancer treatment will have nausea. It can happen right after treatment or a few days later. Ask your doctor about medications that can make you feel better. Also, keep track of when you’re nauseated. You may be able to spot patterns that can help you get ahead of the problem. Also:

  • Eat small meals more often and avoid greasy foods and citrus.
  • Try foods at room temperature instead of very hot or cold.
  • When you’re nauseated, try bland foods like crackers, gelatin, ice chips, rice, plain mashed potatoes, or applesauce.

Call your doctor if you have severe nausea or you’re vomiting a lot. If you throw up, wait an hour before you eat or drink anything. Then, begin with ice chips and gradually add foods. Chamomile, ginger root tea, or ginger ale can sometimes help settle your stomach.

Weakness and Fatigue

Many parts of cancer treatment can make you feel weak or tired, including the treatment itself, worry or depression, not eating, pain, and too few blood cells in your body.

  • Make sure you get enough rest. Sleep at least 8 hours a night, and try to lie down during the day to rest if you’re still tired. Avoid caffeine late in the day.
  • Exercise. Short walks can give you more energy. If you’re more active, you’ll rest better.
  • Save your energy for the things that are really important to you. Get help from family and friends with errands and other chores.
  • If you feel pain, let your doctor know. There are almost always treatments that can help.
  • Eat plenty of iron-rich foods, like lean meat, beans, dark, leafy vegetables, and iron-fortified cereals or pasta.
  • If your body has too few red blood cells, a condition called anemia, your doctor may recommend erythropoietin or darbepoetin, treatments that stimulate bone marrow to make red blood cells. You can get them by injection, which you can sometimes do on your own at home. If you get this treatment, your doctor will watch you to see if you have rashes, allergic reactions, and problems with blood pressure.

Mouth Soreness

Sometimes, breast cancer treatments can make your mouth or throat sore. Check with your doctor or dentist to see what can stop your pain.

  • Ask your doctor about drugs to ease mouth soreness.
  • Choose soft foods that won’t irritate your mouth, such as scrambled eggs, macaroni and cheese, pureed cooked vegetables, and bananas.
  • Cut food into small pieces.
  • Avoid citrus fruits, spicy or salty items, and rough foods.

Hair Loss

Not everyone will lose their hair during cancer treatment. It depends on the type of chemotherapy you get and the dose. Your doctor can tell you if you can expect hair loss.

While some women will notice their hair gets thinner, others will lose it completely, including eyelashes and eyebrows. Sometimes it happens suddenly, or you may have a more gradual loss a few weeks after you start treatment.

Some women prepare by getting a short hair style before chemotherapy begins. You can also try hair wraps and wigs.

When hair grows back, the texture may be different, but many women won’t notice any changes. The good news about hair loss is that it stops once treatment is over. After a few months hair can regrow completely.

Weight Gain

Some women with breast cancer gain weight from:

  • Being less active during treatment
  • Focusing more on eating
  • Medications
  • Depression
  • Hormone changes

If you notice you're gaining weight, let your doctor know and see what they think might help you. Don’t go on a diet on your own -- your body needs a lot of nutrients during breast cancer treatment.

Higher Risk of Infections

Chemotherapy and radiation therapy for breast cancer can stop your body from making white blood cells, which fight infections. Try to stay out of large crowds and away from sick adults and children for 7 to 10 days after you have chemotherapy. That's when you usually have the fewest white blood cells.

Contact your doctor right away if you get sick. They might recommend antibiotics as a precaution. Other doctors suggest women get a flu shot before they start chemotherapy.

If your white blood cell counts are too low, your doctor may give you a treatment called G-CSF (granulocyte colony stimulating factor -- Neulasta or Neupogen) or GM-CSF (granulocyte macrophage colony stimulating factor -- Leukine).


Most types of cancer have the potential to make it harder for you to get pregnant. Your infertility may be temporary or it may be permanent. The severity of your problem may depend on how long you’re on treatment, the dosage, your age, and other things.

Here are some ways that cancer therapies may affect your fertility:

  • Chemotherapy may lower the number of eggs your body releases to be fertilized.
  • Radiation may damage your ovaries and uterus.
  • Hormone therapy may interrupt your menstrual cycles and make it harder to conceive.

If you think you might want to get pregnant after your cancer treatments are done, you may want to talk with your doctor about fertility preservation methods, such as collecting eggs to freeze for later use.

Brain Fog

Some people call this “chemo brain.” But you can have this common kind of mental fog even without chemotherapy, or from other cancer treatments such as radiation, immunotherapy, and hormone therapy. You may notice problems during and after your treatments. There is no proof that these cognitive issues lead to dementia. Symptoms may include:

  • Forgetfulness
  • Trouble concentrating
  • Mild memory loss, such as names and dates
  • Difficulty multitasking

These problems usually go away within 6-12 months after your treatment ends. But some people may have cognitive issues for years.

Emotional Impact

Cancer treatments can affect you mentally as well as physically. For example, treatments can set off inflammatory immune reactions that may lead to depression, anxiety, and other mood changes. You may feel:

  • Irritable
  • Worried
  • Unmotivated
  • Uninterested in sex or other activities
  • Hopeless
  • Anxious

Cancer can be a life-changing diagnosis. Many people have times when they feel overwhelmed emotionally or mentally by it. Talk to your doctor so you can figure out if the symptoms stem from your treatments. Different types of psychotherapy and mental health counseling may help you get through this time.

When Are Side Effects an Emergency?

Call your nurse or doctor if you have:

  • A temperature over 100.4 F. If you have any fever or chills, tell your doctor right away. If you can’t get in touch with your doctor, go to the emergency room.
  • New mouth sores, patches, a swollen tongue, or bleeding gums
  • A dry, burning, scratchy, or "swollen" throat
  • A cough that is new or doesn’t go away
  • Changes in how your bladder works, including a need to go urgently or more often, burning when you pee, or blood in your urine
  • Digestive changes, including heartburn; nausea, vomiting, constipation, or diarrhea that is severe or lasts longer than 2 or 3 days; or blood in your stools

Show Sources

American Cancer Society.

National Cancer Institute: “Fertility Issues in Girls and Women With Cancer,” “Memory or Concentration Problems and Cancer Treatment.”

Current Treatment Options in Oncology: “Maintaining Fertility in Young Women With Breast Cancer.”

Cedars Sinai: “What Is Chemo Brain?

National Comprehensive Cancer Network: “Mood Changes.”

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