RSO (Rick Simpson Oil)

Key Takeaways

• RSO (Rick Simpson Oil) is a highly concentrated, full-spectrum cannabis extract typically containing 60–90% THC

• RSO is not a proven cure for cancer or any other disease — there is insufficient clinical evidence to support such claims

• Manufacturing or possessing RSO without a prescription is illegal in the UK

• Patients interested in high-THC cannabis oil can access pharmaceutical-grade, lab-tested alternatives legally through a Releaf prescription

What Is Rick Simpson Oil (RSO)?

RSO (Rick Simpson Oil) is a highly concentrated, full-spectrum cannabis extract named after Rick Simpson, a Canadian man who publicly promoted homemade cannabis oil in the early 2000s as a treatment for his skin cancer. RSO is typically very high in THC — often containing 60–90% — and is consumed orally in small amounts.

Rick Simpson began producing and distributing his oil in 2003 after claiming it cured his basal cell carcinoma. He published instructions online for making RSO at home using solvent-based extraction (traditionally naphtha or isopropyl alcohol), and the oil gained a significant following within the cannabis advocacy community.

Does RSO Cure Cancer?

RSO is not a proven cure for cancer or any other disease. This is an important distinction that must be stated clearly.

While there is preclinical research suggesting certain cannabinoids may have anti-tumour properties in laboratory and animal settings, according to Cancer Research UK, "there is not enough reliable evidence to prove that cannabis or cannabis oil can treat cancer in humans." The NHS echoes this position.

• Laboratory studies have shown cannabinoids can kill cancer cells in petri dishes — but many substances do this without being effective treatments

• A small number of animal studies have shown some promise, but results have been mixed

• No large-scale clinical trials have demonstrated RSO as an effective cancer treatment

• Replacing or delaying conventional cancer treatment with RSO could have serious consequences

Patients diagnosed with cancer should always follow the treatment plan recommended by their oncology team. Medical cannabis may be prescribed alongside conventional treatment to help manage symptoms such as chronic pain, nausea, and appetite loss.

What Are the Safety Concerns with Homemade RSO?

What Is the Legal Status of RSO in the UK?

Manufacturing RSO at home is illegal in the UK. Possessing cannabis extract without a prescription is an offence under the Misuse of Drugs Act 1971. This applies regardless of the intended purpose, including personal medical use.

However, patients interested in high-THC cannabis oil can access pharmaceutical-grade alternatives legally through a specialist prescription. Since November 2018, cannabis-based products for medicinal use (CBPMs) have been available on prescription in the UK as Schedule 2 controlled substances. Learn more about qualifying conditions for medical cannabis.

How Do Prescribed Cannabis Oils Compare to RSO?

Medical-grade full-spectrum cannabis oils prescribed through Releaf offer the same broad-spectrum cannabinoid benefits that RSO advocates value, but with critical advantages:

• Guaranteed quality — every batch is independently lab-tested

• Precise dosing — exact mg/ml of THC, CBD, and other cannabinoids

• No contamination risk — screened for solvents, pesticides, and heavy metals

• Clinical oversight — prescribed and monitored by a specialist doctor

• Legal — fully compliant with UK law

For patients who have been self-medicating with RSO, transitioning to a legal, quality-controlled prescription offers significantly improved safety. Browse our medical cannabis products to see what's available.

If you've been considering high-THC cannabis oil for your condition, check your eligibility to explore safe, legal, pharmaceutical-grade alternatives.

Frequently Asked Questions

Q: Is Rick Simpson Oil legal in the UK?

A: No. Manufacturing or possessing RSO without a prescription is illegal in the UK under the Misuse of Drugs Act 1971. However, patients can access legal, pharmaceutical-grade high-THC cannabis oil through a specialist prescription.

Q: Can RSO cure cancer?

A: There is no reliable clinical evidence that RSO or any cannabis oil can cure cancer in humans. Patients should never replace conventional cancer treatment with RSO.

Q: What is the difference between RSO and medical cannabis oil?

A: RSO is a homemade, unregulated extract with variable potency and contamination risk. Prescribed medical cannabis oil is pharmaceutical-grade, lab-tested, contaminant-screened, and monitored by a specialist doctor.

Q: Can I get something similar to RSO on prescription?

A: Yes. High-THC, full-spectrum cannabis oils are available on prescription in the UK. These offer a comparable cannabinoid profile to RSO but with guaranteed quality and medical supervision. Your Releaf specialist can discuss appropriate formulations.