What causes it?

There is an area in the brain known as the vomiting centre. When this is stimulated it will make us feel sick or vomit. There are many things that may affect the vomiting centre.


  • Some drugs for pain relief
  • Anaesthetics
  • Antibiotics
  • Some drugs taken by mouth which act on certain cells in the stomach

Cancer treatments


This is usually given over several months. In most cases each treatment is followed by a rest period. Nausea or vomiting may occur a few hours after treatment but sometimes it can start sooner. Generally vomiting stops within 48 hours and nausea within 72 hours. Occasionally sickness may last longer. If this happens contact the hospital or your family doctor (GP).

Some chemotherapy tablets taken at home may also cause sickness. If so, talk to your doctor, nurse or pharmacist about the best time of the day to take them.

Radiotherapy to the abdomen

Very few people experience nausea – it depends on which part of the body is being treated. Some people feel sick at the beginning of a course of treatment and find that nausea often disappears within a day or two. Others start to feel sick later on. Do tell the radiographers or your doctor if you suffer from nausea. You can be given drugs to control it and it is very unlikely that your radiotherapy will need to be suspended. Nausea may continue for a couple of weeks after the end of treatment.

An operation on the stomach or bowel

It is not uncommon to wake up feeling sick. Nausea may last for up to 24 hours, until the effects of the anaesthetic have worn off. Modern anaesthetics, however, cause much less post-operative nausea and vomiting. 

If you have had an operation on your stomach or bowel, you will have a thin tube inserted up your nose and down into your stomach. This is called a nasogastric tube. It will drain off any fluid and stop you from being sick. However, you may still feel nauseous for a few days. The tube won't affect your ability to speak.


  • Movement
  • Pain
  • Raised levels of body chemicals like calcium

Thoughts and feelings

  • Memory of previous treatment, known as 'anticipatory nausea'. If you are worried about this, do talk to your doctor, nurse or any of the staff caring for you. Support can be offered to help you cope with anticipatory sickness.
  • Anxiety
  • Unpleasant thoughts
  • Sights, smells and tastes

If you have had treatment before which made you feel sick or be sick, just the thought of having a similar treatment may make you feel sick, even before you have it. This is called anticipatory nausea and vomiting.

It is quite common in people having several courses of chemotherapy. If there is no obvious reason for your nausea or vomiting, your doctor may ask for some tests to find out the cause.

Remember sickness may be nothing to do with your illness or treatment. You may have picked up a 'tummy bug' or eaten something which has upset your stomach.