Why is medical cannabis so hard to access on the NHS?

On 1 November 2018, medical cannabis was legalised in the UK following high-profile campaigns led by families of children with treatment-resistant epilepsy.

The change in legislation saw medical cannabis moved to Schedule 2 under the Misuse of Drugs Regulations, making it legal to prescribe by doctors on the GMC specialist register. 

Specialists can prescribe cannabis-based products for medicinal use (CBPMs) for any indication where there is considered to be a genuine unmet clinical need, and are typically prescribed for chronic conditions that have not responded to at least two previous treatments. 

Cannabis that is not prescribed by a healthcare professional remains illegal and a Class B drug under UK law.

CBD vs THC

The cannabis plant contains hundreds of different active compounds, which are known as cannabinoids.

The most common and widely studied for their medicinal properties are:

• CBD - non-psychoactive.

• THC - psychoactive and associated with the ‘high’. 

Most products that are available on prescription in the UK contain a combination of CBD and THC, and usually other minor cannabinoids.

Prescribed CBD products are different to those which can be bought online or from high street retailers. These products may only contain up to 1 mg THC per container and have not been through the same testing processes as prescription products.

There are currently three licensed cannabis products in the UK that have received market authorisation from the Medicines and Healthcare Regulatory Agency (MHRA) and have been recommended by the National Institute for Health and Care Excellence (NICE) for prescription on the NHS.

Unlicensed CBPMs have not received MHRA approval and are prescribed as ‘specials’. However, they are still subject to strict regulatory oversight and must be produced in line with EU-GMP standards.

In the seven years since the law change, fewer than six people have been able to obtain an NHS prescription for an unlicensed CBPM, and almost all of these have been for children with treatment-resistant epilepsy.¹

But at the same time, the number of people obtaining private prescriptions has increased significantly. More than 42 specialist cannabis clinics are now registered with the Care Quality Commission in England, prescribing CBPMs to an estimated 90,000-100,000 people.²

In its 2025 annual update, the CQC reported 130% increase in private prescriptions with over 300,000 items dispensed between 2023 and 2024.³

Lack of ‘high-quality’ research and randomised controlled trials 

The vast majority of unlicensed CBPMs have not undergone randomised control trials to determine their safety and efficacy. As a result, many professional medical bodies have called for more high-quality evidence before these can be widely prescribed on the NHS.⁴ 
Regulators such as NICE and the MHRA require medications to have gone through ‘gold standard’ randomised controlled trials (RCTs) to receive market authorisation and recommendation for prescription on the NHS.

And during a debate in the House of Commons on 31 January 2025, Health Minister Karin Smyth said the NHS must have “greater assurance on the clinical and cost-effectiveness of these medicines” before routine prescribing.⁵

A 2019 review into the barriers to prescribing made 10 recommendations designed to widen access, including initiating clinical trials, an observational study, and the establishment of an NHS patient registry, to collect evidence for the safety and efficacy of CBPMs.

In November 2024, the NHS, in collaboration with University College London, announced the first two RCTs investigating isolated forms of CBD and THC in people with severe epilepsy, as recommended in the 2019 review, but these have since been delayed again.⁶ 

Meanwhile, experts have highlighted the challenges and limitations of conducting RCTs on cannabis. 

Real-world evidence collected through patient registries like Drug Science’s T21 suggests people are reporting significant improvements in symptoms and quality of life following treatment with CBPMs, in a range of different conditions.

Lack of training and education for clinicians 

Less than one percent of doctors who are eligible to prescribe CBPMs are actively doing so, and almost all of these are prescribing privately.⁷ 
Whilst it is not uncommon to prescribe other unlicensed medicines on the NHS, factors such as the lack of a clear funding pathway, limited education and training, and a lack of guidance and peer support from medical bodies, prevent many from doing so.

Cannabinoids like CBD and THC work by interacting with receptors in the body’s endocannabinoid system (ECS), which plays a crucial role in regulating physiological systems such as pain, mood, temperature, and immune response.

Yet despite the important role of the ECS in bodily function, it is still not widely taught in medical school. The only training most doctors receive on cannabis is in relation to its use as an illegal, recreational drug. 

Stigma related to cannabis 

This lack of education also contributes to the prevailing stigma around cannabis and its use, even medicinally, which can be linked to longstanding prohibitive drug policies and conservative attitudes towards illegal drugs.

In a survey of 400 cannabis patients at Sapphire Medical Clinics, 84% believed they had been subject to stigma from society.⁸ This includes healthcare professionals, with less than one in four of participants believing their clinicians approved of their CBPM prescription.

Concerns over safety and side effects 

Due to the lack of clinical research on medical cannabis, many still have concerns about long-term safety and adverse effects. Most of the existing studies have been conducted on illegally-sourced cannabis, which hasn’t been tested for strength or other contaminants.

With some studies showing that cannabis can alter the developing brain, the British Paediatric Neurology Association guidelines only recommend the prescription of licensed products like Epidyolex, and do not advise the use of THC in children with treatment-resistant epilepsy. 

Although according to Barnes there is a lack of evidence for their concerns, and clinicians must make decisions in the best interests of the patient, after weighing up both the benefits and the risks. 

These barriers mean that many more people who could potentially benefit from CBPMs are unable to access them due to the cost of a private prescription, with an estimated 1.4 million people using illegal cannabis to manage medical conditions. 

Many of the families of children with epilepsy, whose stories were instrumental in the law change, have still not been able access CBPMs as was promised in 2018. Others are forced to continue spending tens of thousands a year on private prescriptions.