Medical cannabis (and cannabis oils)Overview

"Medical cannabis" is a broad term for any sort of cannabis-based medicine used to relieve symptoms.

Many cannabis-based products are available to buy online, but their quality and content is not known. They may be illegal and potentially dangerous.

Some products that might claim to be medical cannabis, such as "CBD oil" or hemp oil, are available to buy legally as food supplements from health stores. But there's no guarantee these are of good quality or provide any health benefits.

And some cannabis-based products are available on prescription as medicinal cannabis. These are only likely to benefit a very small number of patients.

Can I get a prescription for medical cannabis?

Very few people in England are likely to get a prescription for medical cannabis.

Currently, it is only likely to be prescribed for the following conditions:

  • children and adults with rare, severe forms of epilepsy
  • adults with vomiting or nausea caused by chemotherapy

And it would only be considered when other treatments weren't suitable or hadn't helped.

Epidiolex for children and adults with epilepsy

Epidiolex is a highly purified liquid containing CBD (cannabidiol).

CBD is a chemical substance found in cannabis that has medical benefits.

It won't get you high, because it doesn't contain THC (tetrahydrocannabinol), the chemical in cannabis that makes you high.

Epidiolex is not yet licensed in the UK but is currently going through the licensing system.

In the meantime, the unlicensed medication can be prescribed for patients with Lennox-Gastaut syndrome and Dravet syndrome (both rare forms of epilepsy).

Nabilone for chemotherapy patients

Many people having chemotherapy will have periods where they feel sick or vomit.

Nabilone can be prescribed by a specialist to help relieve these symptoms, but only when other treatments haven't helped or aren't suitable.

Nabilone is a medicine, taken as a capsule, that has been developed to act in a similar way to THC (the chemical in cannabis that makes you high). You may have heard it described as a "manmade form of cannabis".

The medicine has been licensed in the UK. This means it has passed strict quality and safety tests, and is proven to have medical benefit.

Nabiximols (Sativex) for MS

Nabiximols (Sativex) is a cannabis-based medicine that is sprayed into the mouth.

It is licensed in the UK for people with MS-related muscle spasticity that hasn't got better with other treatments.

But its availability on the NHS is limited. The National Institute for Health and Care Excellence (NICE) does not recommend that NHS doctors prescribe Sativex, as it is not cost effective.

Read more from the MS Society on cannabis for MS.

Long-term pain

There is some evidence medical cannabis can help certain types of pain, though this evidence is not yet strong enough to recommend it for pain relief.

What about products available to buy?

Some cannabis-based products are available to buy over the internet without a prescription.

It's likely most of these products – even those called "CBD oils" – will be illegal to possess or supply. There's a good chance they will contain THC, and may not be safe to use.

Health stores sell certain types of "pure CBD". However, there's no guarantee these products will be of good quality.

And they tend to only contain very small amounts of CBD, so it's not clear what effect they would have.

Is medical cannabis safe?

The risks of using cannabis products containing THC (the chemical that gets you high) are not currently clear. That's why clinical trials are needed before they can be used.

"Pure" products that only contain CBD, such as Epidiolex, do not carry these unknown risks linked with THC.

But in reality, most products will contain a certain amount of THC.

The main risks of THC cannabis products are:

  • psychosis – there is evidence that regular cannabis use increases your risk of developing a psychotic illness such as schizophrenia
  • dependency on the medicine – although scientists believe this risk is probably small when its use is controlled and monitored by a specialist doctor

Generally, the more THC the product contains, the greater these risks are.

Cannabis bought illegally off the street, where the quality, ingredients and strength are not known, is the most dangerous form to use.

Read about the risks of regularly smoking cannabis.

What are the side effects?

After taking medical cannabis, it's possible to develop any of the following side effects:

  • decreased appetite
  • diarrhoea
  • feeling sick
  • greater weakness
  • a behavioural or mood change
  • dizziness
  • feeling very tired
  • feeling high
  • hallucinations
  • suicidal thoughts

If you experience any side effects from medical cannabis, report these to your medical team. You can also report them through the Yellow Card Scheme.

CBD and THC can affect how other medicines work. Always discuss possible interactions with your specialist.

CBD can also affect how your liver works, so doctors would need to monitor you regularly.

How do I get a prescription?

You cannot get cannabis-based medicine from your GP – it can only be prescribed by a specialist hospital doctor.

And it is only likely to be prescribed for a small number of patients.

A hospital specialist might consider prescribing medical cannabis if:

  • your child has one of the rare forms of epilepsy that might be helped by medical cannabis
  • you have spasticity from MS and treatments for this aren't helping
  • you have vomiting or feel sick from chemotherapy and anti-sickness treatments aren't helping

The specialist will discuss with you all the other treatment options first, before considering a cannabis-based product.

A prescription for medical cannabis would only be given when it was believed to be in your best interests, and when other treatments hadn't worked or weren't suitable.

It's expected this would only apply to a very small number of people in England.

If the above does not apply to you, do not ask your GP for a referral for medical cannabis.

Will the laws on cannabis be relaxed?

The government has no intention of legalising the use of cannabis for recreational (non-medical) use.

Possessing cannabis is illegal, whatever you're using it for. That includes medical use unless it has been prescribed for you.

More information

Cannabis: the facts.

Page last reviewed: 01/11/2018
Next review due: 01/11/2020