What causes sickness and vomiting?

Some blood cancers can make you feel sick because of the physical and emotional changes they can cause. Some underlying causes are:

Constipation

You may feel sick or vomit if you have constipation (difficulty pooing), or other problems with your bowels.

Liver and kidney damage

If you have liver or kidney problems because of blood cancer or its treatment, waste products can build up in the blood and cause sickness and vomiting.

Hypercalcaemia (too much calcium in your blood)

Sometimes blood cancer can cause calcium to leak into your bloodstream. Too much calcium in the blood is called hypercalcaemia. It can make you feel very thirsty, sick, drowsy and confused. You might also wee a lot and may be constipated. People with myeloma and plasma cell leukaemia are at particular risk of hypercalcaemia, although it can happen in other blood cancers. It is also more likely to happen when cancer is advanced. Hypercalcaemia can be dangerous if left untreated, so speak to your doctor or nurse as soon as you get any symptoms.

Pain

Symptoms of blood cancer can include severe pain. This can make you feel sick or vomit.

Pressure in the brain

Some types of blood cancer can affect your central nervous system and lead to raised pressure in the brain. This may affect the vomiting centre in the brain and make you feel sick or vomit.

Emotional effects

Being very nervous or worried about blood cancer and its treatment can make you feel sick. Sometimes talking about your situation can help to reduce worry and relieve sickness.

Infections and food poisoning

Getting an infection from germs in the environment or food (food poisoning) can make you feel sick or vomit. If you think you have an infection, seek medical advice urgently. Infections can get worse very quickly when you have blood cancer so don’t wait. We have information on infection symptoms and what to do. We also have more information on understanding and managing infection when you have blood cancer.

Advanced cancer

Up to 7 out of 10 (up to 70%) of people with advanced cancer feel sick or vomit. This might be because of the cancer itself or its treatment.

Feeling sick and vomiting are common side effects of some cancer treatments, listed below.

Anti-cancer drugs (chemotherapy, targeted therapies and immunotherapy)

Not all chemotherapy or targeted therapy drugs will make you sick. Some are more likely to make you feel sick than others, but it’s important to remember that everyone is different and will react in a different way. 

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.

If you have chemotherapy or other drugs that are known to cause sickness and vomiting, you’ll be given anti-sickness drugs (anti-emetics) before treatment, and may also take them for a few days after treatment.

Radiotherapy

Radiotherapy uses high energy rays, such as x-rays, to kill cancer cells. Some people have radiotherapy on their whole body (called total body irradiation, or TBI) before a stem cell transplant.

If you have TBI, you’ll probably feel sick if you don’t take anti-sickness drugs. With TBI, you’ll probably have chemotherapy as well, which makes it more likely that you’ll experience some sickness and vomiting.

If you have local radiotherapy to a particular part of your body, it’s only likely to cause sickness and vomiting if it’s given to certain areas such as the brain, stomach, gut or liver.

Mucositis (sore mouth and gut)

Mucositis is a condition that causes inflammation of the mouth and gut. It’s a common side effect of chemotherapy and sometimes radiotherapy. The symptoms will usually stop a few weeks after your treatment has finished. We have more information on mucositis.

Remember, your experience will depend on the treatment you’re having and your personal response to it.

Different people experience sickness and vomiting at different times, some before treatment, some immediately after treatment and some a while later. Cancer Research UK has more information about when you might feel sick because of your treatment.

If you’re worried about side effects from treatment, talk to your hospital team. We have information about talking to your hospital team.

It’s important to know that there’s a range of anti-sickness drugs available. So do tell your treatment team if you feel sick, so they can help you manage this unpleasant side effect.