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Sickness from treatment

Some cancer treatments cause sickness. Read about why this might happen to you and what can be done to help you feel more comfortable.

Sickness and cancer treatments

The treatments most likely to cause sickness are:

  • chemotherapy
  • radiotherapy
  • biological therapies

You feel sick because the vomiting centre in your brain has been triggered. Some cancer drugs act directly on the vomiting centre. Others stimulate nerves in your digestive tract. This releases a chemical called serotonin that sends a message to the vomiting centre.

Anti sickness medicines

Your doctor or nurse will normally give you anti sickness medicines before you start your radiotherapy or cancer drug treatment. These medicines are called anti emetics.

Your anti emetics might control sickness completely, or they could make it milder. 

It's important to take anti sickness medicines regularly if you are taking cancer drug tablets or capsules each day because you could feel slightly sick for as long as you are taking them.

Tell your nurses or medical team if you feel sick at any point in your cancer treatment. They can always do something to help, even if you are already taking anti sickness medicines. Changing the medicine to another type might control your sickness.

Chemotherapy and biological therapies

Not all chemotherapy or biological therapy drugs will make you sick. There is a higher chance of feeling sick with some drugs, but not everyone will have the same amount of sickness with the same drug. Other treatments you are having can also make a difference to how sick you feel.

The dose of drugs and how often you have them might affect how you feel. The higher the dose and the closer they are together, the more likely you are to feel or be sick.

Having a drug into your vein is more likely to make you sick soon after you have it. But tablets may start to make you feel sick an hour or a few hours after you take them because the drug gets into your bloodstream more slowly.

Hormone therapies

Hormone therapy is used mainly to treat prostate and breast cancer. You might also have hormone therapy for womb or kidney cancer.

Some people feel sick when they first start this treatment. Most people affected feel only slightly sick and this usually wears off over the first couple of weeks of taking the tablets.

Let your doctor or nurse know if it does not wear off. They can prescribe anti sickness medicines or change your hormone therapy treatment.


You might have bisphosphonates to lower high calcium levels or to treat a cancer that have spread to the bone. Some types of bisphosphonates can cause sickness. 

Bisphosphonates given into a vein may make you feel sick within an hour of having the treatment. Let your doctor or nurse know if this happens. The sickness can be controlled with anti sickness medicines and usually only lasts a few hours.

You could feel mildly sick if you are taking bisphosphonate tablets or capsules. This can usually be well controlled with anti sickness medicines.

It can also help to sit upright for an hour after taking the tablet. Or your doctor may change the type of bisphosphonate.


Some painkillers can make you feel sick, and in rarer cases may actually make you be sick. 

Morphine type drugs can cause sickness for the first couple of weeks. You might take an anti sickness drug for the first week or so if you start taking strong painkillers.

Once you get used to the painkiller you can usually stop taking the anti sickness drug. You could be given an anti sickness tablet before each dose of your painkiller if you have sickness that does not go away. Or your doctor could try a different painkiller.


You might feel or be sick when you wake up from a general anaesthetic. This happens in about a third of people having surgery (33%). But this depends on:

  • the type of surgery
  • the type of anaesthetic
  • what other drugs you have during the operation

Sickness due to the anaesthetic usually lasts an hour or two after surgery, but for some people this may last up to 24 hours.

If you have had major surgery to your abdomen, your bowel may stop working for a short time. This can allow fluids to build up in your stomach, making you feel sick. With this type of surgery, you may have a tube put into your nose and down into your stomach (nasogastric tube) to help drain the fluid away and stop you being sick. 

Taking strong painkillers after surgery might also make you feel sick.

Your doctor and nurse will make sure you have anti sickness medicines after surgery. Other ways of managing sickness straight after surgery include avoiding sudden movement, and to only drink sips of water to begin with (once you are allowed to drink).


Not all radiotherapy treatment will make you feel or be sick. It depends on the part of your body that is being treated.

About half of people who have radiotherapy to their abdominal area will feel or be sick. This can happen within an hour or two of having your treatment.

It can last up to 6 or 7 hours. Radiotherapy to the brain also tends to cause sickness.

Sickness also depends on your dose of radiotherapy and how often you are having treatment. You're more likely to feel or be sick if you are having one large dose of radiotherapy as opposed to having smaller doses over longer periods of time.

Total body irradiation (TBI)

Total body irradiation (TBI) as part of a bone marrow transplant is very likely to make you feel and be sick if you don't have anti sickness drugs to prevent it. It is likely that you will be having chemotherapy as well if you are having TBI. Having both these treatments makes it more likely that you will have some sickness.

Tell your doctor or nurse if you feel sick. Doctors don't always routinely give anti sickness medicines before radiotherapy because not everyone is sick with this treatment. But if you feel sick, they will give you the medicines.
Last reviewed: 
21 Jan 2015
  • Anticipatory Nausea and Vomiting

    JA Roscoe and others

    Support Care Cancer, 2011

    Volume 19, Issue 10

  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2015

  • Cancer: Principles and practice of oncology (10th edition)
    VT DeVita, S Hellman, SA Rosenberg, TS Lawrence
    Lipincott Williams and Wilkins, 2015

  • Risks associated with your anaesthetic: feeling sick

    Royal College of Anaesthetists, 2013

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