Cannabis for Epilepsy: Benefits, Side Effects and Access in the UK

Alternaleaf Team
Written by
Alternaleaf Team
Aug 29, 2024
Last updated:
Aug 29, 2025

If you’re wondering if medical cannabis for epilepsy is legal in the UK, the answer is yes. It can be prescribed by specialist doctors on the NHS in some circumstances, usually when one of three specific forms of epilepsy are present. 

Since 2018, medical cannabis has been legally available on prescription through licensed clinics like Alternaleaf for 50+ conditions, and it’s much more widely available through this route than through the NHS. You can find out if you’re eligible by completing the quick eligibility checker on our website. 

Cannabis-based medicines for epilepsy can be made from one or more natural compounds that come from the cannabis plant. We’re exploring two of the cannabinoids used in medical cannabis for epilepsy, the benefits and side effects, to give you a better understanding of how it works.

What is Medical Cannabis? 

The term ‘medical cannabis’ encompasses any sort of cannabis-based medicine (flower, oils, extracts) that comes from a part, or parts of the cannabis plant, and is used to relieve symptoms. 

The cannabis plant contains hundreds of natural chemicals, and when it comes to treating epilepsy, cannabidiol (CBD) and tetrahydrocannabinol (THC) are the two most important. These are cannabinoids - substances that act on cells in the body to cause effect.

One of the biggest benefits of CBD for epilepsy is that it does not have the mood-altering effects often associated with cannabis. There has been a lot of research around the benefits of CBD for epilepsy treatment, and the potential it has to help people with this condition.

More research is needed when it comes to THC and epilepsy, to find out the effects of THC and epilepsy treatment, and if products containing it are safe. THC is commonly known as the part of the cannabis plant that can make people feel ‘high’, but also has strong medicinal use cases.

How cannabis helps with epilepsy 

For roughly 30% of people with epilepsy, conventional treatments do not work to control seizures. When this is the case, it is not unusual to consider medical cannabis as an option. Studies have shown the benefit of certain plant-based CBD products in treating specific groups of people with epilepsy.

Cannabis as a medicine has been used since as early as 2800 BC, but there’s been limited science behind why or how it works with the body. However, a 2023 study led by researchers at NYU Grossman School of Medicine, reveals a previously unknown way in which (CBD) reduces seizures. 

A molecule called lysophosphatidylinositol (LPI), found in brain cells called neurons, is thought to amplify nerve signals as part of normal function. But these signals can be hijacked by disease to promote seizures. 

The new study found that CBD can block signals carried by LPI, preventing seizures. 

Approved cannabis-based medicines for epilepsy 

Currently Epidyolex is the only cannabis-based medicine for epilepsy that has been approved in the UK for prescription on the NHS. It contains pure CBD, does not contain any THC, and was approved by the FDA in June 2018.

CBD has shown some positive effects on certain bodily systems and is effective in reducing seizures in some people with epilepsy. 

In a recent study without a placebo control, 214 people received Epidyolex and completed 12 weeks or more on the drug. During the study, seizures decreased by an average of 54%.

There is good evidence that suggests Epidyolex as an add-on treatment option reduces seizures for people with Tuberous sclerosis complex (TSC), Dravet syndrome and Lennox-Gastaut syndrome. For the latter two types of epilepsy, Epidyolex must be used alongside clobazam.

The above applies to adults and children aged two or over, and only if their seizures are not well controlled after trying two or more epilepsy medicines.

One thing to note is The National Institute for Health and Care Excellence (NICE), an organisation that makes recommendations about what medicines doctors can prescribe on the NHS, say doctors should check the frequency of seizures every 6 months. If Epidyolex is not reducing seizures, treatment should be stopped.

Using THC for epilepsy treatment isn’t as straight-forward. 

Specialists can legally prescribe THC for epilepsy treatment; however it is on a case-by-case basis and self-referring patients will need to supply evidence of a diagnosis and previous treatments. 

For a small number of children with severe epilepsy in the UK, unlicensed cannabis oil containing CBD and THC has been used as a treatment. Although there is some evidence that suggests these medicines may be effective, so far the research has been limited and of low quality.

Until there’s enough evidence to show the medicine is safe and effective, and there are no licensed medicines that would be suitable instead, NICE will not make any recommendations prescribing medicines containing both CBD and THC for epilepsy treatment. 

Can people with other types of epilepsy get a prescription for Epidyolex?

Currently, Epidyolex is only recommended as a treatment on the NHS for people with TSC, Dravet syndrome and Lennox-Gastaut syndrome due to good evidence that it reduces seizures for people with these conditions.

Whilst there is some evidence that Epidyolex may be effective for other types of epilepsy, it isn’t great. Specialists can still prescribe it on a case-by-case basis, but it’s likely it would only be in exceptional circumstances, where other treatments have not worked.

Some people might be able to access Epidyolex by taking part in clinical trials. This is because NICE has called for more research into using CBD for epilepsy treatment on other types of severe, treatment-resistant epilepsies. 

Potential side-effects when using medical cannabis for epilepsy 

Just like any other medicine, Epidyolex can cause side-effects. The most common happen to more than 1 in 10 people, and include:

  • Feeling drowsy or sleepy
  • Having less appetite for food
  • Diarrhoea
  • Fever
  • Being sick

Other side effects can be: 

  • Change in liver function
  • Malaise
  • Fatigue 
  • Asthenia (weakness or lack of energy)
  • Rash
  • Insomnia
  • Sleep disorder
  • Poor quality sleep
  • Infections

FAQs

Does medical cannabis help with seizures?

As we’ve shown above, there’s evidence to back the benefits of medical cannabis treatment for seizures. For example, this study shows CBD can be effective in reducing seizures in some people with epilepsy. In another recent study without a placebo control, 214 people received Epidyolex and completed 12 weeks or more on the drug. During the study, seizures decreased by an average of 54%. Another great benefit of CBD is that it has fewer, and less extreme, side effects compared to traditional medications. This is simply incredible. Why? Because it shows how CBD can massively improve quality of life for someone who suffers from seizures.

Also, keep in mind that a combination of cannabinoids along with other active compounds like terpenes (the part of any plant that produces the smell) and flavonoids, can work together to potentially produce different effects. This phenomenon is known as the entourage effect

What are the potential therapeutic effects of medical cannabis for epileptics?

  • Reduce seizure frequency 
  • Improve seizure control 
  • Improve quality of life 
  • Improve tolerance to conventional anti-seizure medications
  • Anti-inflammatory and antioxidant properties
  • There’s some preclinical evidence that suggests CBD may protect neurons from damage during seizures

Should you worry about drug interactions?

Medical cannabis is no different from traditional medications, and there is a possibility it will interact with other medications that you may be taking for epilepsy such as Epidyolex UK. So, you should always be aware of potential drug interactions: they can affect how medications or supplements work, increase side effects, or reduce effectiveness. Always consult your clinician or a healthcare provider before combining treatments or starting your medical cannabis journey.

Summary

There is no standard procedure when using cannabis-based medicines for epilepsy. From how the body reacts to the type of epilepsy already present, every case and every person is different. But there’s no denying the benefits when it is effective – reducing seizures and improving quality of life. 

Cannabidiol (CBD) and tetrahydrocannabinol (THC) are the two chemicals to look out for, with Epidyolex being the only cannabis-based medicines for epilepsy currently approved in the UK, which contains pure CBD. NICE will not make any recommendations prescribing medicines containing CBD and THC for epilepsy treatment due to a lack of evidence showing the medicine is safe and effective. 

However, for those who suffer with epilepsy and are unable to access these treatments on the NHS, you may be able to self refer to a licenced medical cannabis clinic, such as Alternaleaf. These clinics currently prescribe medical cannabis products, containing both THC and CBD, for over 50+ conditions.

If you have a diagnosis, and have been previously offered at least two treatments for this condition, it is likely that you may qualify for a medical cannabis prescription. The best thing to do is speak to your clinician, or seek the help of a licensed medical cannabis clinic like Alternaleaf if you’re considering medical cannabis treatment. Find out if you’re eligible by heading to our website and completing our 30 second eligibility checker