What causes nausea and vomiting during cancer treatment

Treatment for cancer can cause Nausea, which is one of the most common side effects. Depending on certain factors, these symptoms can be mild or severe. The following factors may increase your likelihood of experiencing nausea, but every individual responds differently to treatment.

If one or more of the following applies to you, you may be more vulnerable

  • You're a woman.
  • You've experienced nausea and vomiting with previous treatments, or you have a history of motion sickness.
  • You have a history of drinking little or no alcohol.
  • You experienced morning sickness during pregnancy.
  • You're younger than 50.
  • You have a high level of anxiety.
  • You are prone to vomiting when you're sick.


It is always important to inform your doctor if you are feeling nauseous or vomiting, regardless of how mild the symptoms may be. 

Mild nausea and vomiting can be uncomfortable but does not usually harm your health. On the other hand, vomiting a lot can cause health problems, such as dehydration, weight loss and fatigueFeeling nauseous or vomiting, regardless of how mild it is, should always be reported to your doctor. This is so they can monitor any health problems that may occur and help find the right anti sickness medicine for you. 

Why Does Nausea Occur?

The reasons why cancer drugs cause sickness are complex, but we do know that some processes in the brain, spinal cord, stomach and small bowel can cause nausea. These processes involve strong drugs that your body sees as a foreigner, which sets off warning signals in your brain and digestive system, by creating chemicals that make you queasy.

The warning signals affect a part of the brain called the vomiting centre, which controls nausea and vomiting. Different things can stimulate the vomiting centre and cause you to feel sick.

It may be stimulated by:

  • Nerves in the gut (stomach)
  • Another part of the brain called the chemoreceptor trigger zone (CTZ)
  • The inner ear, which is caused by body motion
  • Our senses – for example, taste, smell and pain
  • Our emotions – for example, if we are scared or nervous.

Drugs that cause sickness

Drugs that can cause sickness are below but always remember everyone reacts differently to each treatment. 

  • Chemotherapy drugs
  • Targeted cancer drugs
  • Immunotherapy
  • Hormone therapies
  • Bisphosphonates
  • Painkillers

Speak to your health care team

Starting treatment and experiencing side effects is very daunting, but you can lower your anxiety by asking the right questions. This will teach you what you need to know and how to handle any situation. 

  • Is this cancer treatment likely to cause nausea and vomiting? If so, when could those side effects start?
  • Is there a way to prevent these side effects of cancer treatment?
  • Who should I tell if I start experiencing nausea or vomiting?
  • How can my nausea be relieved if it starts?
  • Do you think certain anti-nausea medicines will work better for me? Why?
  • What are signs that nausea and vomiting are affecting my hydration or nutrition?
  • Should I tell you right away if my anti sickness medicine is not relieving my symptoms?
  • Do these recommended anti sickness medicines have any side effects I should know about?

Keep track of your nausea

Many health concerns can be caused by nausea and vomiting, making cancer treatment and side effects even more difficult. You can prevent health concerns from developing by tracking your symptoms every day. 

Start by simply creating a table or using a calendar. To make this quick and easy you can use my number system below. Make sure you write down how many times you threw up, if you were able to eat and drink and if you went to treatment that day.

  Nausea Level  Food & Drink  Treatment day?  Notes 
Mon 1
Tue 2 - V 3 Treatment day  Particular foods are making me feel ill. 
Wed 3
Thur 3 - V

Number Systems

 Food and drink 
1 - No nausea 
2 - Mild nausea 
3 - Moderate nausea 
4 - Severe nausea 
5 - Extreme nausea 
V for if you have thrown up. 
1 - Eating & drinking well.
2 - Some struggle but able to eat & drink small amounts.
3 - Struggling to eat and drink.
4 - Can not eat or drink anything.


Check out our fatigue diary too! - 'How to create a fatigue diary'