THC talk: How much THC is too much?

With a surge of patients in the UK turning to prescribed cannabis oil and prescribed cannabis flowers to manage their chronic pain, anxiety, poor sleep or low mood, dialogue surrounding THC has become more prominent in general conversation, in medical circles, and in mainstream media outlets. 

While tetrahydrocannabinol (THC) is known to have therapeutic potentials such as pain relieving properties to sedative effects, it is also the compound that’s responsible for cannabis’ psychoactive, or intoxicating, effects. Therefore, there is an element of risk with its use, and, it is a substance that can be misused. 

But, while CBPMs like medical cannabis flower and prescribed cannabis oil remain available only through private healthcare providers like Releaf in the UK, its likely publicly funded healthcare regulators do not see creating a specific legislation that determines the maximum THC limit for these treatments as a top priority. And so, almost seven years post legalisation, this still hasn’t been done. 

However, that doesn’t mean private medical cannabis clinics are unregulated. At Releaf, each and every clinical application of THC is overseen, and monitored by, a qualified healthcare professional, and dosages are carefully titrated to ensure maximum benefit with minimal risks.

Let’s dive into the details: 

Is THC legal in the UK?

Since 2018, products containing THC and CBD have been available on prescription in the UK for a variety of different health conditions when first-line treatments have proven unsuccessful. While the recreational use of cannabis and THC remains illegal, medical cannabis was legalised after an evidentiary review conducted by Professor Dame Sally Davis, who at the time was the Chief Medical Officer to the British Government, concluded: 

“There is clear evidence from highly respected and trusted research institutions that some cannabis-based medicinal products have therapeutic benefits for some conditions…
As Schedule 1 drugs by definition have little or no therapeutic potential, it is therefore now clear that from a scientific point of view keeping cannabis-based medicinal products in Schedule 1 is very difficult to defend.”

Nonetheless, the question ‘how much THC is too much?’ still very much exists, and, experts are sharing their concerns over the lack of gold-standard clinical evidence for products that contain high levels of THC. 

What does the evidence say about THC?

While there are thousands of real-world case studies, patient accounts, literature reviews, and patient response surveys that suggest THC can be beneficial in managing a number of different conditions, there are relatively few robust randomised controlled trials (the ‘gold standard’ research that is used to prove a medications safety and efficacy) that demonstrate the same, powerful results. 

Some argue this is because historically, cannabis has been pushed from pillar to post when trying to solidify funding for high quality, large scale research studies into its therapeutic effects because of the stigma associated with its recreational uses. Others cite the large amount of variables in natural substances like cannabis as the main crux of the issue, but regardless of the reasoning, it cannot be denied that in the world of modern medicine, research into cannabis based treatments is still very much in its infancy stages. 

However, with innovative developments occurring in the medical cannabis manufacturing industry, hopefully a lack of RCT data will become a thing of the past, as the technologies being pioneered and implemented by the likes of SOMAÌ pharmaceuticals and Glass Pharms, allow standardisation and consistency across each batch of products, with rigorous quality controls in place to determine cannabinoid concentrations.

Still, until this evidence is available, exercising caution is critical. 

So, how much THC is too much?

Because THC has the ability to directly interact with the pathways in the brain, it's critical that when people are using it to benefit their health - it actually does benefit their health, and it doesn’t come with a compromise. And while THC has no known fatal overdose threshold, unlike other substances like opioids, fentanyl, or even paracetamol, that doesn’t mean high doses come without risk.

Short term acute side effects of THC can include anxiety and paranoia, as well as cognitive, memory or coordination impairment, and more severe risks have been established. This includes things like cannabis-induced psychosis, hyperemesis, and an increased risk of experiencing a cardiac event. 

This leads to the age-old question ‘how much THC is too much?’ and quite honestly, the answer is different for everyone. Tolerance, product formulation, delivery method, and underlying health conditions all play a role in how THC affects an individual, and therefore, making a hard and fast decision on what constitutes a high THC dose for any and all patients can be tricky.

What is the THC limit for medical cannabis?

At the moment, there is no official legal cap on THC strength in medical cannabis, but there have been calls from the Care Quality Commission for clinical practices like this to be standardised, and for medical cannabis clinics to follow emerging best practice guidance.

In the last year both The Cannabis Industry Council, and The Medical Cannabis Clinicians Society, have published Good Practice Guides specifically for prescribing cannabis based treatments in the UK. In the MCCS guidance, they state:

“There is a tendency for some patients to request a flower with a high THC content, even up to 30%. However, flowers with very high THC flowers will naturally have fewer minor cannabinoids and terpenes, potentially reducing their medical value. Research in this area is currently limited. 

We recommend that a prescription drug over 22% THC by weight should be approved by peers before being prescribed. Additionally, high THC doses should not be prescribed initially, but increased over time, if indicated, with careful documentation of the effects.”

At the moment, there are UK clinics that prescribe medical cannabis cultivars containing over 30% THC, and in other territories like Australia, extracts containing as much as 80% THC can be prescribed. But, here at Releaf we believe caution is key, and as a result we have been extensively selective when establishing our formulary, capping the treatments we prescribe at 25% THC. 

Releaf’s approach to responsible prescribing

As well as capping the treatments in our formulary at 25%, we’ve also established a rigorous screening and triage process to assess a patient's suitability for medical cannabis before starting treatment, to rule out any contraindications or possible complications.

In order for us to do this, all patients need to do is use the integrated NHS login tool in our sign-up flow to grant us instant access to their medical records, so we can review their health history before their first appointment. 

We have also developed stringent prescribing guidelines in line with the MCCS and CIC guidance, as well as the guidelines implemented by the NHS, the National Institute for Health and Care Excellence, and the General Medical Council, for after a patient's initial consultation. 

All our clinicians attend a daily multidisciplinary meeting (MDT) to discuss any new, complex, or cases requiring high volumes of medication with the rest of the prescribing team, to ensure clinical compliance, and collective, expert insight. 

A final word from Graham Woodward, Releaf’s Chief Operating Officer, and Specialist Advisor to the CQC: 

“Releaf does not prescribe any pseudo-recreational products, and we agree that such medications are detrimental to the industry. 

In fact, despite being the UK’s fastest growing medical cannabis clinic we’ve got one of the smallest formularies in the industry, as we’re very strict about not stocking medications that are sold in other territories for any kind of recreational use.

Around 80% of all prescriptions issued by Releaf are for either products grown by Glass-Pharms, a Home Office and MHRA regulated state-of-the-art facility, here in the UK, or for SOMAÌ medical cannabis oils, which are manufactured to the highest standards in their GMP regulated facility based in Portugal.”


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