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Side Effects

Understanding Nausea and Vomiting

Nausea can be described as having a sick or uncomfortable feeling in the back of your throat and stomach. There are many other words describing the feeling of nausea, including "sick to one's stomach", "queasy", or "upset stomach". Other symptoms can happen at the same time as nausea, such as increased saliva (spit), dizziness, light-headedness, trouble swallowing, skin temperature changes, and a fast heart rate.

Vomiting is also described as “throwing up.” Nausea can lead to vomiting, and sometimes nausea and vomiting happen at the same time, but they can be totally separate problems, too. When you vomit, your stomach muscles contract (squeeze) and push the contents of your stomach (liquids and food) out through your mouth.

Retching is when your body tries to vomit without bringing anything up from your stomach. Other words used to describe retching are gagging or having the dry heaves.

What causes nausea and vomiting in people with cancer?

Nausea and/or vomiting in the person with cancer can be caused by many different things, such as:

  • Cancer treatments
  • The cancer itself, especially if it’s in or affecting the brain or abdomen (belly)
  • Other medicines given for health problems that are not cancer-related
  • Bowel slowdown or blockage (obstruction)
  • Constipation
  • Inner ear problems
  • An imbalance of minerals and salts (electrolytes) in the blood
  • Infections
  • Anxiety
  • The expectation of vomiting because of vomiting before in the same setting (this is called anticipatory vomiting)
  • Other diseases or illnesses

Not all people who get cancer treatments have nausea and/or vomiting. Your risk for having nausea or vomiting depends on the type of cancer being treated and the type and dose of treatment being given.

Chemotherapy and other drugs used to treat cancer travel throughout the body while radiation therapy treats one part of the body where the cancer is located. For this reason, chemotherapy and some other drugs used for cancer treatment cause more nausea and vomiting than radiation therapy. If you are getting chemotherapy, you might hear your cancer care team refer to it as chemotherapy-induced nausea and vomiting (CINV). Your cancer care team knows which treatments have a higher risk for CINV because studies have shown that certain drugs used to treat cancer are more likely to cause nausea and vomiting than other others. Chemo and other drugs used to treat cancer are classified according to their emetogenic potential (how likely the drug will cause nausea or vomiting) as high, moderate, low, or minimal risk. Anti-nausea drugs are used to help control and even prevent nausea and vomiting depending on this risk. You may hear them called anti-emetics.

Every person with cancer who’s getting treatments that cause nausea or vomiting can, and should, get medicines to keep this from happening or to control it. Talk to your doctor for more information or if you have questions about your risk for nausea and vomiting.

What makes nausea and vomiting occur?

The exact way that nausea and vomiting occur is still not fully understood, but studies have shown a pathway in the brain that is triggered and sends signals to make it happen. When you are given cancer treatment that can cause nausea:

  • A certain area of the brain is triggered and sends signals to other parts of the body
  • Certain areas of the esophagus (the tube that connects the mouth to the stomach), stomach, small intestine, and large intestine are triggered
  • These triggers activate a reflex pathway that leads to nausea and vomiting
  • Anti-nausea (anti-emetic) drugs to block different parts of this pathway can be used to control and prevent nausea and vomiting.

Health problems caused by nausea and vomiting

Nausea and vomiting are some of the most unpleasant side effects of cancer treatment, but they have become less of a concern due to more effective treatment for them. They rarely become life-threatening.

Still, nausea and vomiting can make it hard to get the nutrition your body needs. Nausea can make you not want to eat or drink anything, and repeated vomiting can lead to dehydration, which is a lack of fluids and minerals your body needs. If nausea and vomiting persist, they can quickly become a serious problem. Be sure to let your cancer care team know right away if either of these happen:

  • You can’t keep fluids down
  • You’re vomiting for 24 hours or longer

Vomiting can also cause tiredness (fatigue), trouble concentrating, slow wound healing, weight loss, and loss of appetite. It can interfere with your ability to take care of yourself and may lead to changes in your treatment plan.

Questions to ask about nausea and vomiting

Ask your cancer care team these questions:

  • Is my cancer treatment likely to cause nausea and vomiting?
  • Can my nausea and vomiting be prevented or controlled?
  • How will you decide which anti-nausea/vomiting treatments I should use?
  • How much will the anti-nausea medications cost?
  • Do the anti-nausea/vomiting treatments you want me to use have side effects?
  • When and how often should I take each medicine?
  • What will we do if the treatment doesn’t control my nausea and vomiting?
  • At what point do I need to call if I still feel nausea or still vomit after taking the medicine?

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

Blanchard EM, Hesketh PJ. Nausea and vomiting. In DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 11th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2019:2078-2085. 

Brant JM, Stringer LH. Chemotherapy-Induced nausea and vomiting. In Brown CG, ed. A Guide to Oncology Symptom Management. 2nd ed. Pittsburgh, PA: Oncology Nursing Society; 2015:171-196.  

Cancer.Net. Nausea and vomiting. 2018. Accessed at -physical-side-effects/nausea-and-vomiting on September 5, 2019.

Hainsworth JD. Nausea and vomiting. In Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020: 599-606.e3.

National Cancer Institute (NIH). Treatment-related nausea and vomiting (PDQ®)- Health Professional Version. 2018. Accessed at on September 6, 2019.

Last Revised: February 1, 2020

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