Understanding Nausea and Vomiting

Nausea is a subjective unpleasant feeling in the back of your throat and stomach that may lead to vomiting. There are many words that describe nausea including sick to my stomach, queasy, or upset stomach. Nausea can have other symptoms that happen at the same time, 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.” When you vomit, your stomach muscles contract (squeeze) and push the contents of your stomach out through your mouth. You might or might not feel nauseated.

Retching is when you try to vomit without bringing anything up from your stomach. Other words used to describe retching are gagging or dry heaves.

Nausea and vomiting often happen at the same time, but they can be 2 different problems.

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:

  • Chemotherapy (also called chemo)
  • Radiation therapy
  • The cancer itself, especially if it’s in or affecting the brain
  • Certain other (non-chemo) medicines
  • 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 due to past vomiting in the same setting (this is called anticipatory vomiting)
  • Other diseases or illnesses

How does nausea and vomiting occur?

Doctors think that vomiting is most likely controlled by the part of the brain called the vomiting center. Less is known about how nausea occurs. When you are given chemo, 2 things happen:

  • A certain area of the brain is triggered
  • 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. Drugs can be used to block different parts of this pathway to control and prevent nausea and vomiting.

Are nausea and vomiting common in people with cancer?

Some chemotherapy drugs are more likely to cause nausea and vomiting than other others. Doctors classify chemo drugs according to their emetogenic potential (how likely the drug will cause nausea or vomiting) as high, moderate, low, or minimal risk. Drugs are used to help control and even prevent nausea and vomiting depending on this risk.

Drugs used to control these side effects are called anti-nausea/vomiting drugs. You may also 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.

What health problems can nausea and vomiting cause?

Nausea and vomiting are 2 of the most dreaded, unpleasant side effects of cancer treatment, but they only rarely become life-threatening.

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

  • You can’t keep fluids down
  • You can’t take the medicines you need
  • 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.

What should I ask my cancer care team 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?
  • 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 the treatment isn’t working?

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 journalists, editors, and translators with extensive experience in medical writing.

National Cancer Institute. Nausea and Vomiting PDQ® last modified 1/4/2016. Accessed at www.cancer.gov/cancertopics/pdq/supportivecare/nausea/Patient on April 5, 2016.

National Comprehensive Cancer Network. AntiemesisNCCN Clinical Practice Guidelines in Oncology – v.2.2016. Accessed at www.nccn.org/professionals/physician_gls/f_guidelines.asp#supportive on April 19, 2016.

Last Medical Review: June 9, 2016 Last Revised: June 9, 2016

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