Cannabis and Cancer

There are different types of cannabis you might have heard can help with the side effects of your treatment. The first is the recreational drug cannabis, also known as marijuana, weed and hash. The second is cannabis oil.


You might have seen stories in the news or online about cannabis being used to treat the side effects of cancer, and even cure it. But this has not been proven through controlled clinical trials.

Cannabis may have an effect in treating some types of cancer. But it could make other types of cancer grow or spread more quickly. There are also health risks with using cannabis, especially alongside your treatment.

It is illegal to possess or supply cannabis in the UK.

Cannabis and chemotherapy

Cannabis can affect how your body processes some chemotherapy drugs. This can cause serious side effects.

You should talk to your doctor if you are thinking about using recreational drugs during chemotherapy.

There are cannabis-based medicines which can be prescribed to help with side effects like feeling or being sick. These can only be prescribed to adults by a specialist when other treatments have not helped or are unsuitable.

Cannabis and radiotherapy

There is very little information about how cannabis affects radiotherapy. However, using cannabis always carries health risks.

You should talk to your doctor if you are thinking about using recreational drugs during radiotherapy.

Cannabis oil

Cannabis oil products contain cannabidiol and are available to buy online. Many of these are still illegal to possess or supply because they also contain THC.

CBD oil does not contain THC and can be bought as a food supplement in the UK. CBD oil can affect some cancer treatments.

Buying any cannabis product online is risky. You may be targeted by scammers. There is also no way to know for sure what is in what you are buying.

Additional risks

Although people have been using cannabis for years, it is not without risks. Cannabis can increase heart rate and interact with other drugs in the body.

You should always get medical advice before using cannabis products. Your pharmacist can give you confidential advice about how medicines, treatments and drugs affect each other.

If you’d like to know more, Cancer Research UK’s Science Blog clearly sums up research into cannabis and the evidence so far.


Published May 2023
Next review 2027

You might also want to read

Alcohol and cancer treatment

Here's what you need to know about alcohol and treatment

Find out more
A teenager with cancer looks out of a window

Complementary therapies

Complementary therapies can be used alongside treatment. Here's what you need to know.

Find out more

Contacts for your emotions and mental health

Useful organisations, resources, apps and communities for emotional and mental health support.

Find out more
A teenager with cancer looks out of a window

Related Topics