Experts Explain: Hypertension and medical cannabis

With an estimated 30% of UK adults (roughly 16 million people) living with high blood pressure, and a large chunk of those being undiagnosed (up to five million), hypertension deserves far more attention than it often receives. 

One of the ‘quieter’ health concerns, hypertension can steadily raise the risk of heart attacks, strokes, kidney disease and other serious complications, and unfortunately, this frequently happens without any obvious symptoms.

At Releaf, “How does medical cannabis affect blood pressure?” is one of the more common questions we hear from new patients, but the honest answer is, it depends. Every patient is different, and the effects of prescribed medical cannabis can and do vary depending on a range of factors.

With World Hypertension Day passing by a few short weeks ago, and to continue our Experts Explain blog series, we spoke with Dr Lorenzo Bernaudo, a consultant surgeon at Releaf, about all things medical cannabis and hypertension. 

Here’s what he had to say:

Why isn’t medical cannabis prescribed to treat high blood pressure in the UK?

“The main reason is that, right now, we lack robust studies and strong scientific medical evidence to justify the efficacy or potential of medical cannabis to treat hypertension. In medicine, if we don't have definitive medical evidence from approved, well-conducted clinical trials, we simply cannot treat a condition.”

Do you think this could this change in future?

“At the moment, there is still a lack of evidence, but I’m confident that in the near future, we’ll see progress. Medical cannabis treatment and research are constantly evolving. It's still a young field, but new studies come out every year. 

Hopefully, in the next year or so, we’ll develop guidelines to help clinicians approach patients with hypertension in a safe and structured way.”

Can medical cannabis be prescribed to people with high blood pressure in the UK?

“The short answer is yes, but this is decided on a case-by-case basis. If the patient's hypertension is well-controlled and has been for a good while, and there are no comorbidities or complications, then yes, medical cannabis treatment can be carefully considered.

But if a patient has extremely high (or low) blood pressure, or blood pressure that's been fluctuating heavily, that would be a red flag. If they had a recent stroke or heart attack, for example, or they're on multiple blood pressure medications, we take a much more conservative approach.”

How does high blood pressure affect a patient’s eligibility during consultation?

“A patient’s medical history always matters, but that’s especially true when it comes to high blood pressure.

When someone with hypertension is being considered for a medical cannabis prescription with Releaf, the first step is to fully understand how well their blood pressure is controlled and how long they’ve had hypertension for. 

We also look at the broader cardiovascular picture. 

High blood pressure on its own isn’t always a barrier, but recent bouts of angina or a heart attack can be. Conditions like diabetes or kidney disease often show up alongside hypertension, so we check for those too.

Some people do really well with medical cannabis, even if they’ve had high blood pressure for years. Others will be more sensitive. That’s why every single case has to be judged individually. 

We look at the medications, the wider health context, and how well the person is managing their condition, along with keeping their current clinical team or GP up to date with any and all changes.”

So, what format of medical cannabis is usually prescribed to patients with hypertension?

“We usually start with oil for two reasons. First, because it enters the bloodstream gradually, which gives a slower onset and potentially more stable effects. Second, oils give us more flexibility to use a balanced formulation, not too high in THC or CBD.

If a patient has a history of hypertension that’s been difficult to manage, we would always start with a balanced oil. Flower is still an option, but it is mostly reserved for patients whose blood pressure has been stable for years or who have used medical cannabis before without issues.

The problem is that flower often has higher THC levels, which can lead to spikes in heart rate and blood pressure. So, oil is our first-line option, and flower is cautiously considered depending on the patient’s medical history and how they respond to the first few months of treatment through Releaf.”

Is that because of the THC?

“Yes, primarily. 

The interaction between cannabis and the cardiovascular system is mostly related to THC. CBD is usually well tolerated. It may lower blood pressure in some people, but the effects are generally more subtle.

One thing that all prospective patients need to understand is that medical cannabis isn't a one-size-fits-all solution.

Some patients do really well with medical cannabis, even if they’ve had high blood pressure issues for years. Others are more sensitive to the side effects that can, and sometimes do, occur from THC administration. 

The last thing we want is for patients to start treatment without a full understanding of the potential, albeit uncommon, cardiovascular effects.” 

Are there any known interactions between cannabis and blood pressure medications?

“Yes, and it is something we take seriously. 

Cannabis has been (tentatively) shown to interact with blood pressure medications in two main ways: through its effects on the body (pharmacodynamics) and through how the body processes medication (pharmacokinetics).

Pharmacodynamically, THC and CBD can behave quite differently once they are absorbed into the bloodstream. THC can raise blood pressure and heart rate, while CBD tends to have a more calming effect, lowering both. Depending on the cannabinoid profile of a product, those effects can either balance each other out, or not. 

When talking pharmacokinetics, cannabis may affect how certain drugs are metabolised in the liver, particularly via a group of enzymes known as CYP450. Much of the available and often prescribed blood pressure medications rely on this system, so if cannabis affects it, the medication could become stronger, weaker, or take longer to work.

Some drugs are taken in an inactive form and only become active after liver metabolism. If cannabis disrupts that process, the medication may not work as intended.

We still need more clinical research to fully understand these interactions, but the potential impact is enough to warrant close oversight, especially when patients are taking multiple medications.

Do you ever adjust cannabis treatment based on blood pressure medication?

“We work very closely with patients’ GPs. That collaboration is a key part of how we manage care safely.

Every time we take on a new patient at Releaf, we send an update letter to their GP. The GP can contact the Releaf clinical team in real time if they have concerns or need clarification. This open channel of communication allows us to co-manage the patient’s treatment effectively, especially when there are complex issues like blood pressure involved.

This ongoing relationship with the patient’s regular healthcare team is essential. It helps ensure that medical cannabis fits safely into their broader treatment plan.

The GP is notified not just when a patient becomes a Releaf patient, but throughout the entire treatment process. If we change anything on our end, we always let the GP know.  That way, they’re always aware of what’s being prescribed and can advise or intervene if needed.”

Are patients expected to monitor their blood pressure while using medical cannabis?

“Yes, we definitely recommend so.  

We always recommend home monitoring, especially during the first few weeks. It gives us a clearer picture of how the patient is responding and helps identify any early warning signs. Monitoring at home is similar to what a GP would advise, and most people can get a monitor easily.

It comes down to common sense. If there are no side effects, checking once a week is enough. But if any do appear, the patient should monitor more frequently and book another consultation with Releaf to discuss.

Our standard procedure is to schedule the first follow-up consultation 30 days after their initial consultation, and then we meet every 120 days throughout their treatment plan. But patients don’t need to wait. If they have concerns, they can contact us at any time. That’s part of our care model. We want all Releaf patients to be fully supported, and we’ve built a responsive team to make that happen.

The Patient Support Team stays in contact and helps flag anything that might need clinical attention. If someone is unsure about their dose or experiencing side effects, we’re here. 

Patients can easily reach Releaf whenever they need support. Whether it's through live chat on our website, by phone, or via email, our team is always available to help.”

Why do patients respond so differently to cannabis?

“Medical cannabis treatment is very personal and highly individual. Conventional medications are designed to work more broadly across large populations, once they’re approved. With cannabis, each person responds slightly differently.

The endocannabinoid system is incredibly complex. Unlike many of the conventional pharmaceuticals commonly prescribed, which usually act on a single known target, medical cannabis interacts with a wide network of receptors throughout the body. It’s more like a vast highway system than a straight road, and that’s why patient responses can vary so much.

As our understanding deepens, I am sure that treatments with more precise and predictable effects will become available. But for now, it still involves careful observation and individual adjustment.”

Safe, supported access to UK medical cannabis treatment for patients with hypertension

As Dr Bernaudo has explained, medical cannabis is not prescribed purely for hypertension in the UK. But patients suffering from a wide range of chronic conditions (including pain, mental health concerns, sleep disorders, neurological conditions, and more) may still be eligible for treatment, even if they also have high blood pressure.

Rest assured, at Releaf, no two patients are treated the same. 

Our world-class clinical team looks at your full health history (including how well any blood pressure issues have been controlled) before making any decisions on whether a prescription for medical cannabis may be suitable and potentially beneficial.

If you’re living with hypertension and wondering whether medical cannabis could help, the best place to start is by checking your eligibility. You can use our fast and free medical cannabis eligibility checker, or chat to our Patient Support Team if you’d prefer to talk things through first.