CBD oil and immunotherapy: what patients need to know

What is CBD oil, and how does it work in the body?

CBD, or cannabidiol, is a phytocannabinoid that typically makes up to 40% of the cannabinoid content of the cannabis and hemp plants. From the perspective of UK law, one of its most important properties is its lack of intoxicating qualities.

In the UK, most CBD products are derived from the hemp plant, which has naturally high CBD levels and minimal to zero THC. This makes hemp-based CBD widely available, but most of these do not fall under the same regulatory umbrella as medical grade CBD prescribed by specialist clinics. 

Prescription medical cannabis products in the UK are manufactured to strict standards, ensuring consistency of dose, purity, and clinical oversight. This distinction matters for cancer patients, as quality and monitoring are essential when CBD is being used alongside treatments such as immunotherapy.

CBD, the endocannabinoid system, and cancer care pathways

CBD can engage with the body’s endocannabinoid system (ECS), a vast regulatory network that helps maintain balance in processes such as pain perception, appetite, mood, sleep, and immune response. While CBD does not bind to either receptor in the same way that THC can with CB1, it can indirectly influence both CB1 and CB2 activity. This modulation helps the ECS maintain balance and may enhance its ability to regulate inflammation, immune responses, and nervous system signalling.

The ECS includes cannabinoid receptors, endocannabinoids produced by the body, and the enzymes that regulate them. CB1 receptors are mainly located in the brain and central nervous system, while CB2 receptors are concentrated in the immune system and peripheral tissues.

Beyond the ECS, CBD also interacts with other signalling pathways. It can influence serotonin (5-HT1A) receptors involved in mood and nausea, TRPV1 receptors linked to pain, and adenosine receptors which regulate inflammation. These interactions contribute to the wide range of effects observed with CBD, such as anti-inflammatory, analgesic, anxiolytic and antioxidant properties.

Key properties of CBD oil in cancer care

These interactions help explain the wide range of effects observed with CBD, including its ability to reduce inflammation, relieve pain, ease anxiety, and protect cells from oxidative stress. For people living with cancer, these properties may offer additional support when managing symptoms or the side effects of treatment.

In the UK, there is an important distinction between over-the-counter hemp-derived CBD products, which contain less than 0.2% THC, and prescription CBD oils available through clinics such as Releaf. Prescription options are medical grade, carefully monitored, and supported by specialist guidance to ensure safe use alongside cancer treatments like immunotherapy.

How does immunotherapy work for cancer patients?

Immunotherapy utilises the body’s own immune system to combat and eliminate cancer cells. Unlike chemotherapy and radiation, which attack cancer cells directly, immunotherapy works by strengthening the immune system’s ability to recognise and respond to them.

Checkpoint inhibitors work by blocking proteins that would otherwise suppress immune responses, allowing T cells to attack tumours more effectively. CAR-T cell therapy modifies a patient’s T cells in the laboratory so they can better recognise and destroy cancer cells. Cytokine therapy stimulates the immune system by introducing molecules that enhance its anti-cancer response.

One of the most significant advantages of immunotherapy is its ability to achieve long-term remission and durable responses. It also tends to be more targeted and specific, often resulting in fewer adverse effects than chemotherapy.

In the UK, access depends on the type of cancer and treatment stage. Some immunotherapies are available through the NHS, while others are only offered privately or through clinical trials. Patients who pursue complementary support such as medical cannabis should do so under supervision to ensure safe integration with their immunotherapy plan.

Why immunotherapy patients may consider CBD

CBD’s ability to ease pain, support appetite, reduce anxiety, and improve sleep makes it a supportive option that many patients consider during immunotherapy. While evidence is still emerging, some people find that CBD helps them cope with the side effects of both their treatment and their cancer, improving overall quality of life when used under medical guidance.

What does the research say about CBD oil and immunotherapy?

Although studies specifically investigating the combined effects of CBD oil and immunotherapy are still limited, there is growing interest in their potential synergistic effects. Research suggests that CBD’s anti-inflammatory and immunomodulatory properties may enhance immune responses and help create a tumour microenvironment that is less favourable to cancer growth.

Preclinical studies also indicate that CBD has anti-tumour properties in certain cancer models. It may inhibit tumour growth, induce programmed cell death, and reduce the spread of cancer cells. These findings suggest that CBD could complement the effects of immunotherapy by supporting the immune system while also directly influencing cancer cell survival.

However, not all evidence points in the same direction. Some patient cohorts have shown reduced response rates to immunotherapy among cannabis users, though the findings are not conclusive and may be influenced by study limitations. This highlights the need for further clinical trials before firm conclusions can be drawn.

Mechanisms of CBD that may support immunotherapy

Several mechanisms may explain why CBD could support immunotherapy. Research has shown that CBD can regulate the immune response and enhance the activity of T cells and natural killer cells, both of which are essential for identifying and eliminating cancer cells.

CBD also possesses strong anti-inflammatory effects. By reducing inflammation, it may help create a more favourable tumour environment for immunotherapy to work effectively.

In addition, CBD has been shown in preclinical models to trigger apoptosis (programmed cancer cell death), slow proliferation, and inhibit angiogenesis, the formation of new blood vessels that feed tumours. Together, these processes suggest potential synergy between CBD and immunotherapy, although most of the evidence remains at the laboratory stage rather than in human trials.

How do cannabinoids work together in cancer care?

THC and CBD take on different roles in cancer care. THC is often more effective for improving appetite, easing persistent pain, and supporting sleep. CBD is better known for helping with mood, calming anxiety, and reducing nausea.

Terpenes, the natural aromatic compounds in cannabis, may add therapeutic effects of their own, such as anti-inflammatory or calming properties.

This combination is known as the entourage effect. It suggests that whole-plant medicines containing THC, CBD, and terpenes may provide broader relief than CBD alone. For some patients, a balanced prescription that brings these elements together offers more effective support during cancer treatment.

For a wider overview of how medical cannabis supports people with cancer, see Medical cannabis and cancer: an updated guide for UK patients

Common side effects and interactions to consider

CBD is generally very well tolerated, but some patients experience side effects such as drowsiness, dry mouth, or changes in appetite. These are usually mild, but should still be monitored.

More importantly, CBD can interact with other medications, including immunotherapy drugs and anticoagulants. A 2024 review in PMC highlighted potential immunosuppressive effects and impaired T-cell activity in some settings.

For anyone undergoing cancer treatment, the safest approach is to always disclose CBD use to the oncology team. This allows doctors to monitor for side effects, check for drug interactions, and adjust treatment plans if needed.

How can UK patients access CBD oil alongside immunotherapy?

In the UK, access depends on whether a product is bought over the counter or prescribed as medical cannabis. Over-the-counter CBD oils are derived from hemp that produces less than 0.2% THC, and the container of whatever CBD product is being sold must have less than 1 mg of THC. They are widely available but not medical grade (they come under the FSA’s Novel Food Items regulations), meaning their quality and consistency isn’t the same as medical grade products.

By contrast, prescription CBD oils supplied through clinics like Releaf are tightly regulated, medical grade, and always monitored by specialists. This ensures safe use alongside treatments such as immunotherapy.

At Releaf, patients are supported from the first consultation through to ongoing care. Our world-class clinical team includes more than 30 specialists, backed by 30+ fully UK-based Patient Support Team staff. Prescriptions are managed through a bespoke Patient Dashboard, which handles ordering, repeat prescriptions, and delivery. Patients also receive a medical cannabis card for protection and easier access.

We were the first clinic to offer domestically grown medical cannabis flower to UK patients through our partnership with Glass Pharms®. This supply chain ensures sustainable and reliable access, and we also stock a wide range of products from the best local and international medical cannabis suppliers.

Patients can choose between flexible PAYG or the Releaf+ membership (£39.99 per month, including unlimited follow-ups, free repeats, free delivery, and member pricing).This pathway ensures that CBD is always supervised by a clinical team, not self-medicated, reducing risks and making treatment safer.

Talking to your doctor about CBD and immunotherapy

Seeking guidance from healthcare professionals before adding CBD oil to an immunotherapy plan is essential. Patients should feel comfortable discussing dosage, possible drug interactions, and how treatment will be monitored.

CBD should never be viewed as a replacement for immunotherapy, but it may have a supportive role in easing side effects and improving quality of life. Openness with the oncology team ensures that treatment remains safe and coordinated.

If you want to speak to a specialist led team that understands exactly what medical cannabis offer, head to our fast and free medical cannabis eligibility checker. 

Releaf - Let's Rethink Healthcare

How does CBD oil compare with other cancer treatments?

Unlike conventional therapies such as chemotherapy or radiotherapy, which directly attack cancer cells, CBD is supportive, not curative. Its role is to help patients manage symptoms, not reduce tumour size. 

There is some emerging research into CBD’s potential to enhance radiation treatment, but overall the evidence for synergy with other cancer therapies remains limited and sometimes conflicting. For now, CBD is best understood as a complementary/adjunct option that should only ever be used alongside standard therapies.

Appetite and cachexia support

Cachexia, or cancer-related weight loss, affects 60 to 80% of people with advanced cancer. It is linked to loss of strength, reduced treatment tolerance, and poorer outcomes.

THC has been shown to stimulate appetite and, in some trials, support modest weight gain. CBD does not directly increase hunger, but may make eating easier by reducing nausea and easing anxiety. 

When combined, THC and CBD has been shown to help cancer patients maintain a more regular diet, which is crucial during treatment.

FAQs about CBD oil and immunotherapy

Is CBD oil safe during cancer treatment?

CBD is generally well tolerated, but safety depends on the context. Some patients experience mild side effects such as fatigue, dry mouth, or appetite changes. CBD can also interact with certain cancer medicines, which is why medical supervision is essential during treatment.

Can CBD interfere with immunotherapy drugs like Keytruda?

There is some evidence that cannabis may influence immune function in ways that could affect checkpoint inhibitors such as Keytruda. Research findings are mixed, and more clinical trials are needed. For now, it is best to use CBD only under supervision and always disclose it to your oncology team.

Can CBD be used with chemotherapy and immunotherapy together?

Preclinical studies suggest CBD may ease side effects and even support the effectiveness of certain therapies, but the clinical evidence is limited. Because CBD can interact with both chemotherapy and immunotherapy medicines, it should only be used under medical guidance.

What medications does CBD interfere with?

CBD can interact with a range of drugs, including immunotherapy medicines and anticoagulants. These interactions may alter how well treatments work or increase side effects. Patients should always disclose CBD use so that doctors can manage any potential risks.

Does CBD oil affect immunotherapy outcomes?

Some clinical evidence suggests cannabis use may reduce response rates to immunotherapy, while other research points to potential benefits. The picture remains unclear, which is why more trials are underway. 

Is CBD available on the NHS for cancer patients?

Currently, NHS prescriptions for cannabis-based medicines in cancer care are limited to chemotherapy-induced nausea and vomiting, and even then they are rare. For all other uses, including CBD for symptom relief during immunotherapy, prescriptions are only available privately through clinics like Releaf.

Conclusion: CBD oil and immunotherapy in the UK

CBD oil is not a silver bullet, but for patients on immunotherapy it can sometimes make the road a little smoother. By easing pain, steadying anxiety, calming nausea, or helping with sleep, it may give the body and mind more room to cope with demanding treatment. The science is still evolving, but the interest from both researchers and patients shows no sign of slowing down.

Safety matters most here. Over-the-counter oils can be unpredictable, but prescribed options are medical grade and supervised by a clinical team. 

That’s exactly what you get when you become a Releaf patient - properly regulated medical cannabis products with ongoing clinical supervision and support. 

If you are considering CBD oil alongside cancer treatment, try Releaf’s medical cannabis eligibility checker. It is free, takes less than 20 seconds, and gives you a clear first step towards seeing if treatment may be suitable.