RSO (Rick Simpson Oil) is a thick cannabis extract with high THC content. No clinical trial has shown that RSO cures cancer in people, and the FDA has not approved it as a cancer treatment. Some patients use it for symptom relief such as pain, nausea, and appetite loss, and many oncology teams ask that they continue standard treatment at the same time.
What is RSO oil?
RSO is a full-extract cannabis oil made by soaking cannabis plant material in a solvent such as isopropyl alcohol, ethanol, or naphtha, then evaporating the solvent to leave a sticky resin. It is named after Rick Simpson, a Canadian who began promoting it in 2003.
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The finished oil is far stronger than typical dispensary products. THC content can range from 50% to 80% or more, and one grain-of-rice-size dose can be enough to alter mood and coordination in a new user.
- Color and texture: dark green to black, thick, tar-like
- Main active compounds: THC, with smaller amounts of CBD, CBG, and terpenes
- Common use: swallowed, or mixed into food or a capsule. Some people apply it to the skin.
Does RSO oil cure cancer?
There is no reliable evidence that RSO oil cures cancer in humans. Lab studies show that THC and CBD can kill some cancer cells in dishes and slow tumor growth in mice, but those results have not carried over into controlled trials in patients. Reviews of the human literature find that cannabinoids help with symptoms, not with shrinking tumors.
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What lab studies show
Preclinical work (cells in a dish, animal models) reports that cannabinoids can trigger cell death and block blood vessel growth in tumors. Those experiments use purified compounds at controlled doses, often delivered straight to the tumor. That setup does not match swallowing an oil, where the drug passes through the liver and reaches tumors at unknown levels.
What human studies show
Human trials of cannabinoids in cancer have focused on nausea, vomiting, pain, sleep, and appetite. The strongest evidence covers chemotherapy-induced nausea, where a prescription cannabinoid product beat older anti-nausea drugs in some trials. No trial has measured RSO against tumor size or survival.
What RSO may help with
Some patients report relief from cancer-related symptoms and from side effects of treatment. This is plausible because THC and CBD act on the same receptors that control nausea, pain signaling, and appetite.
- Chemotherapy nausea and vomiting (the best-documented use)
- Chronic cancer pain, as an add-on to opioids
- Appetite loss and weight loss
- Anxiety and trouble sleeping
Relief of symptoms is not the same as treating the disease. RSO does not appear to replace surgery, radiation, chemotherapy, immunotherapy, or targeted therapy.
Risks and side effects of RSO
High-THC oil produces strong effects, and the gap between a helpful dose and a bad experience is narrow.
- Dizziness, confusion, and loss of coordination
- Racing heart and drops in blood pressure
- Anxiety, paranoia, or panic, which is more common in new users
- Drowsiness and falls, a real risk for older patients
- Interactions with blood thinners, sedatives, and some chemo drugs processed by liver enzymes
Contamination is a separate concern. Home-made oil can carry leftover solvent, pesticides, or mold. Products sold online without lab testing may contain synthetic cannabinoids or no THC at all.
Call your oncology team if you feel faint, have chest pain, or cannot stay awake. Do not stop cancer treatment to try RSO, since delays in proven therapy can cut the chance of control or cure.
Is RSO legal in the US?
Legal status depends on your state. Medical cannabis is legal in most states, and adult-use cannabis is legal in a smaller number. RSO is not a prescription drug, so you buy it as a state-regulated cannabis product, not from a pharmacy.
Federal law still lists cannabis as a Schedule I controlled substance, which creates gaps in banking, insurance, and interstate transport. Taking RSO across state lines, even between two legal states, is a federal offense.
How do patients use RSO?
Most guidance from clinicians and dispensaries follows the same start-low pattern. There is no standard medical dose, and the "full gram in 90 days" protocol promoted online is not based on trial data.
- Talk to your oncologist or an oncology pharmacist first, and bring a list of every drug and supplement you take.
- Start with a dose the size of a half grain of rice, once a day, in the evening.
- Wait 2 to 3 hours before judging the effect. Swallowed oil takes hours to peak and lasts a long time.
- Increase by small steps every few days, and stop increasing when side effects appear.
- Keep a written log of dose, time, and symptoms so your team can adjust other medicines.
Convenience shapes what people stick with. Pre-filled syringes, capsules, and tinctures cost more per milligram than raw resin, but they make dose tracking simpler than scraping oil from a tube.
Buy from a licensed dispensary that posts third-party lab results for potency and contaminants. Ask which solvent was used and whether the batch was tested for pesticides.
Questions to ask your oncology team
- Could cannabis interact with my chemo, immunotherapy, or blood thinner?
- Are my nausea, pain, or appetite problems better handled by adjusting my current medicines?
- Does my treatment plan leave room for a cannabis trial without delaying anything?
- Who monitors me if I have a bad reaction?
Bottom line
RSO is a high-THC cannabis extract with a real role in symptom relief for some patients and no proven role in curing cancer. Treat claims of a cure with skepticism, keep your oncology team informed, and do not swap proven treatment for an unproven oil. If you try it, start low, buy lab-tested product, and watch for interactions.