Few cannabis products generate as much passionate debate as Rick Simpson Oil. To its advocates, RSO is a miracle cure — particularly for cancer. To the medical establishment, it is an unproven product backed by anecdotes rather than clinical evidence. The truth, as with most things in cannabis, is more nuanced than either side suggests.

This page aims to give you an honest, balanced picture of what RSO is, what the evidence does and does not support, and what you should know if you are considering using it.

What Is RSO?

RSO (Rick Simpson Oil) is a thick, dark, tar-like full-spectrum weed concentrate — sometimes called marijuana oil or cannabis oil — made by soaking cannabis plant material in a solvent, typically ethanol or isopropyl alcohol, and then evaporating the solvent, leaving behind a concentrated oil.

Key characteristics of RSO:

• Extremely potent. RSO typically contains 60 to 90% THC, making it one of the most concentrated marijuana extracts available. A single gram of RSO may contain 600 to 900 mg of THC — this will get you very high even in small amounts.
• Full-spectrum. Unlike THC isolate or distillate, RSO retains the full range of cannabinoids (THC, CBD, CBN, CBG, and others), terpenes, flavonoids, and other plant compounds present in the source material. Proponents believe this full-spectrum profile is essential to its purported benefits.
• Typically consumed orally. Unlike most concentrates, RSO is not usually smoked or vaporized. It is most often eaten — placed on food, in capsules, or applied under the tongue.
• Dark and viscous. Its appearance resembles thick, dark molasses or tar. The dark color comes from the full-spectrum extraction process, which pulls out chlorophyll and other plant matter along with the cannabinoids.

The History of RSO

RSO is named after Rick Simpson, a Canadian engineer who claims to have cured his own basal cell carcinoma (a type of skin cancer) in 2003 by applying a homemade cannabis oil extract directly to the cancerous skin lesion. Simpson reported that the lesion disappeared within days.

After his experience, Simpson became a vocal advocate for cannabis oil as a cancer treatment. He shared his extraction method freely, produced a documentary film (Run From the Cure), and encouraged others to make and use RSO for cancer and other serious conditions.

How RSO Differs from Other Cannabis Concentrates

The concentrate market is crowded, so it is worth understanding what makes RSO distinct:

• Full-spectrum vs. refined. Most weed concentrates (distillate, shatter, wax) are refined to isolate specific cannabinoids or achieve maximum potency. RSO deliberately retains the full chemical profile of the plant. This is a meaningful distinction if you believe in the entourage effect.
• Oral consumption vs. inhalation. Most concentrates are designed to be dabbed or vaporized. RSO is designed to be eaten or absorbed sublingually, which means it undergoes first-pass liver metabolism and produces longer-lasting, often more intense effects.
• Medical positioning. RSO is specifically marketed and discussed in the context of serious medical conditions, particularly cancer. Other concentrates are marketed for both recreational and medicinal use.
• DIY origins. RSO originated as a homemade product with a freely shared recipe. While it is now produced by licensed manufacturers in legal markets, it retains a grassroots, patient-driven identity distinct from the corporate concentrate market.

The Cancer Claims — What the Evidence Actually Shows

This is the section that matters most, and it requires honesty. RSO is most widely discussed as a cancer treatment. Here is what the science actually says, layer by layer:

Lab Studies (In Vitro)

It is true that cannabinoids — including THC, CBD, and others — have been shown to kill cancer cells in laboratory settings. Multiple studies have demonstrated that cannabinoids can trigger apoptosis (programmed cell death) in various cancer cell lines, inhibit tumor cell proliferation, and reduce angiogenesis (the formation of new blood vessels that tumors need to grow).

A comprehensive review in <em>Molecular Cancer Therapeutics</em> documented that cannabinoids can induce apoptosis in tumor cells, inhibit tumor angiogenesis, and reduce tumor cell migration in laboratory and animal models across multiple cancer types including glioma, breast, prostate, and lung cancer.

Velasco et al., Molecular Cancer Therapeutics, 2012

Animal Studies

Animal studies have shown some promise. Cannabinoids have reduced tumor growth in mice with certain types of cancer, including gliomas (brain tumors) and breast cancer models. Some studies have shown cannabinoids working synergistically with conventional chemotherapy agents.

These results are genuinely encouraging and justify further research. But animal models do not always translate to humans — the history of cancer research is full of treatments that worked in mice but failed in human trials.

Human Clinical Trials

As of now, there are no completed, published clinical trials in humans demonstrating that RSO — or any cannabis product — cures cancer. A small number of early-phase trials are investigating cannabinoids as adjunct treatments (used alongside conventional therapy), but results are preliminary and do not support using cannabis as a standalone cancer treatment.

What Cannabis CAN Do for Cancer Patients

While the evidence for cannabis curing cancer is lacking, the evidence for cannabis helping cancer patients is much stronger:

• Nausea and vomiting. Synthetic cannabinoids (dronabinol, nabilone) are FDA-approved for chemotherapy-induced nausea and vomiting. Whole-plant cannabis is widely used for the same purpose.
• Appetite stimulation. Cancer and chemotherapy frequently cause severe appetite loss. THC is well-documented as an appetite stimulant, and dronabinol is FDA-approved for AIDS-related wasting (a similar appetite-loss scenario).
• Pain management. Cancer-related pain, including neuropathic pain from chemotherapy, may respond to cannabis. See our Chronic Pain page.
• Anxiety and sleep. A cancer diagnosis is profoundly stressful. Cannabis may help manage the anxiety, insomnia, and emotional distress that accompany cancer treatment.
• Quality of life. Multiple surveys and observational studies report that cancer patients using cannabis experience improved overall quality of life.

A systematic review in <em>BMJ Supportive &amp; Palliative Care</em> found that cannabis-based medicines showed benefit for chemotherapy-induced nausea and vomiting, cancer-related pain, and appetite stimulation, though evidence quality varied and more rigorous trials were needed.

Bonn-Miller et al., BMJ Supportive & Palliative Care, 2021

How People Use RSO

If you are considering RSO for any purpose, understanding how it is typically used can help you make informed decisions:

Administration

• Oral consumption is the most common method. RSO is placed on a small piece of food (a cracker, a piece of bread), mixed into a capsule, or swallowed directly. Because it undergoes first-pass liver metabolism, the effects are similar to edibles: slow onset (30 minutes to 2 hours), intense effects, and long duration (4 to 8+ hours).
• Sublingual absorption — placing RSO under the tongue — provides somewhat faster onset than swallowing, as some THC is absorbed directly through the mucous membranes.
• Topical application to the skin is how Rick Simpson originally claims to have used it for his skin cancer. Some people apply RSO to skin conditions, though the evidence for topical use is very limited.

Dosing

RSO dosing starts extremely small and increases gradually:

• Starting dose: A rice grain–sized amount, which equals approximately 25 mg of THC. For context, a standard weed edible is 5 to 10 mg. Even this starting dose is substantial for someone without THC tolerance and will get you very high.
• Titration: Doses are typically increased slowly over days to weeks, with users gradually building tolerance to the psychoactive effects.
• The "Simpson Protocol": Rick Simpson’s recommended protocol involves building up to 1 gram of RSO per day (600 to 900 mg THC per day) over the course of several weeks, consuming 60 grams total over approximately 90 days. This is an extraordinarily high dose — roughly 60 to 90 times the standard edible dose — and will produce profound intoxication, heavy sedation, and significant impairment, especially in the early stages before tolerance develops.

Safety Considerations

• Extreme potency. RSO is one of the most concentrated marijuana extracts available. Accidental overconsumption can result in severe intoxication lasting many hours — intense anxiety, paranoia, disorientation, nausea, and incapacitation. While not fatal, this is a genuinely miserable experience.
• Residual solvents. Homemade RSO may contain residual isopropyl alcohol or other solvents if the extraction and evaporation process is not performed correctly. Consuming residual solvents is a legitimate health hazard. This is one of the strongest arguments for buying RSO from licensed producers with lab-tested products.
• No standardization. RSO is not a regulated pharmaceutical product. Potency, cannabinoid ratios, and terpene profiles vary enormously between batches and producers. Without lab testing, you do not know exactly what you are taking.
• Cannabis use disorder risk. The Simpson Protocol involves consuming extremely high doses of THC daily for months. This level of use carries a significant risk of developing cannabis use disorder (dependence). Stopping after prolonged, high-dose use may produce uncomfortable withdrawal symptoms including insomnia, irritability, reduced appetite, and anxiety.
• Drug interactions. THC and other cannabinoids are metabolized by the CYP450 liver enzyme system and can interact with many medications, including some chemotherapy drugs, blood thinners, and immunosuppressants. If you are being treated for cancer or any serious condition, drug interactions are a real and potentially dangerous concern. See our Drug Interactions page.
• Cardiovascular risk. High-dose THC increases heart rate and may pose risks for people with cardiovascular conditions. See our Cardiovascular Risks page.
• Impairment. The Simpson Protocol effectively means being significantly impaired for weeks to months. This has real implications for work, driving, caregiving responsibilities, and quality of life during treatment.

If You Choose to Use RSO

We are not here to make your decisions for you. If you have weighed the evidence and decided to use RSO, here is how to do so as safely as possible:

• Buy from a licensed dispensary that provides lab-tested products with Certificates of Analysis. This ensures you know the potency and that the product is free from residual solvents, pesticides, and contaminants. Do not make RSO at home — the extraction process involves highly flammable solvents and carries fire and explosion risk.
• Start with the smallest possible dose. Even if your goal is to eventually reach higher doses, begin with no more than a rice grain–sized amount and stay at that dose for several days before increasing.
• Tell your oncologist or primary care doctor. Even if you believe they will be dismissive, your medical team needs to know what you are taking. Drug interactions with cancer treatments are a real risk, and your doctor cannot monitor for them if they do not know about the RSO.
• Do NOT stop conventional treatments. If you are undergoing cancer treatment, RSO should be used as a complement — never as a replacement. Continuing chemotherapy, radiation, or immunotherapy while adding RSO is a reasonable choice. Stopping proven treatments in favor of RSO alone is not.
• Keep a detailed journal. Track your doses, effects, side effects, and any changes in symptoms or lab work. This data is useful for you, your doctor, and contributes to our collective understanding. See our Journaling & Tracking guide.
• Be honest with yourself about the evidence. Hope is powerful and necessary, especially during a cancer diagnosis. But hope should be informed by reality. RSO may provide symptom relief and quality-of-life improvements. Whether it has anti-tumor effects in living humans remains unproven.

Legal Status

RSO is legal to purchase and possess wherever cannabis is legal. In states with medical cannabis programs, RSO is commonly available at dispensaries. In states with only recreational programs, it is typically available to adults 21 and over. In states and countries where cannabis remains illegal, RSO is also illegal.

RSO is not FDA-approved for any medical condition. No cannabis-derived product (other than Epidiolex for epilepsy and the synthetic cannabinoids dronabinol and nabilone) has received FDA approval. This means RSO cannot be legally marketed as a treatment or cure for cancer or any other disease.