Ultimate Guide to RSO (Rick Simpson Oil)

Updated October 2026

Introduction: What Is RSO?

RSO (Rick Simpson Oil) is a thick, dark, high-THC cannabis oil made by soaking cannabis flower in a solvent such as food-grade ethanol, straining it, and evaporating the solvent off. The result is a tar-like full extract cannabis oil (FECO) that keeps most of the plant’s cannabinoids and terpenes. It’s usually swallowed or applied to the skin, not smoked.

It’s named after Canadian engineer Rick Simpson, who promoted the oil in the early 2000s after claiming it cleared up his skin cancer, a claim never confirmed by clinical research.

Unlike CBD oils or distillates, RSO is highly potent, often with very high levels of THC.

Today, RSO is sold in many state dispensaries, usually in oral syringes. Scientific evidence on RSO itself is very limited.

This guide covers what RSO is, where it came from, how it’s made and taken, the types available, what the research shows, side effects, legality, and where to buy it.

The Origins of RSO

Who Is Rick Simpson?

Rick Simpson was working as an engineer in Canada when he suffered a serious head injury in 1997. He has said cannabis helped when other medications didn’t.

Around 2003, after being diagnosed with basal cell carcinoma (a common skin cancer), he applied a homemade cannabis extract to spots on his skin and later claimed they disappeared (Healthline overview of RSO).

That account was never scientifically verified. Simpson shared his recipe for free, the story spread online and through documentaries, and the oil became known as Rick Simpson Oil (RSO).

What Makes RSO Unique?

• High THC Content: Most RSO is made from THC-rich strains, often 60–90% THC.
• Full-Spectrum: Unlike CBD isolate or THC distillate, RSO keeps the full plant profile.
• Thick Consistency: Sticky, tar-like oil stored in syringes or jars.
• How It’s Used: Traditionally swallowed or applied to the skin, not smoked or vaped.

RSO vs Other Cannabis Products

It’s easy to confuse RSO with other cannabis extracts. Here’s how it compares:

Key takeaway: RSO is not CBD oil. Most RSO is strongly intoxicating; if you don’t want a high, CBD products are a different category.

What the Research Says About RSO

Disclaimer: RSO is not FDA-approved, and this page is not medical advice. Research is ongoing; talk to a clinician before using any cannabis product for a health condition.

Why People Use RSO

• Its history: RSO became famous through Simpson’s personal story, not clinical trials.
• The format: It’s an oral, high-THC product measured in small amounts by syringe, so some people choose it over smoking.
• Personal reports: Users describe strong, long-lasting, sedating effects. These are anecdotes, not evidence that RSO treats any condition.

Scientific Evidence

• No approval as a cancer treatment: The National Cancer Institute states that the FDA has not approved cannabis or cannabinoids for use as a cancer treatment (NCI PDQ, Cannabis and Cannabinoids).
• Human studies are limited: NCI says small studies have been done, with results unreported or pointing to a need for larger studies.
• Lab and animal studies are not proof that a product works or is safe in people.
• Approved cannabinoid drugs exist for chemotherapy-related nausea and vomiting, per NCI. RSO is not one of them.

Expert Insight

“RSO has always been one of the most talked-about cannabis extracts because of its potency and full-spectrum profile. At Cannabis Training University, we emphasize that while many patients share positive experiences with RSO, it should be approached with caution, education, and respect for its strength. Always start low, go slow, and buy from a trusted source.”
— Jeff Zorn, CEO of Cannabis Training University

How to Make RSO at Home

Fire, Ventilation and Legal Warning: Do this legally, only where permitted. Some states and cities restrict or ban home extraction even where cannabis itself is legal, so check your state and local law first. Ethanol is flammable, and its vapor can ignite from a spark, pilot light, gas stove, or cigarette. Work outdoors or with strong ventilation, use electric heat only, keep every open flame and spark source away, and keep a fire extinguisher within reach. Use only food-grade ethanol. Never use butane, naphtha, lighter fluid, or any other hydrocarbon solvent at home. Many people buy lab-tested RSO from a licensed dispensary instead.

The ethanol method below is shown for education. It is the only method we cover for home use. Extraction with other solvents belongs in a licensed, purpose-built facility, not a home. To study extraction in more depth, see CTU’s Cannabis Extraction course.

Ingredients & Tools

• 1 oz dried cannabis (usually high-THC)
• Food-grade ethanol only (never butane, naphtha, lighter fluid, or any other hydrocarbon solvent)
• Large glass/stainless steel container
• Coffee filter or cheesecloth
• Electric rice cooker (electric heat only; never a gas stove or open flame)
• Glass jars or syringes for storage
• A fire extinguisher, and an outdoor or very well-ventilated work area

Step-by-Step Process

1. Check the law and set up safely: Confirm home extraction is permitted where you live. Work outdoors or with strong ventilation, away from flames, pilot lights, sparks, and anyone smoking.
2. Prepare cannabis: Break into small pieces.
3. Ethanol wash: Cover with food-grade ethanol, stir for 2–3 minutes.
4. Strain: Filter into a clean container.
5. Evaporate the ethanol: Heat gently in the electric rice cooker, with no open flame and plenty of airflow so vapor can’t build up, until most liquid is gone. Never leave it unattended.
6. Purge: Allow bubbles to stop forming, a sign that most of the ethanol is gone.
7. Store: Thick oil is collected in syringes or jars.

Yield: 1 ounce of cannabis produces about 3–4 grams of RSO depending on potency. Homemade oil isn’t lab-tested for potency or leftover ethanol.

Types of RSO

RSO isn’t just one product. It comes in different forms:

• RSO Syringes: Most common format. The syringe makes small amounts easier to measure.
• RSO Capsules: Pre-measured amounts with no mess, often preferred by beginners.
• RSO Tincture: Diluted with carrier oils, easier to take under the tongue.
• RSO Edibles: Infused into gummies or chocolates. Longer-lasting effects.
• RSO Topicals: Applied directly to the skin.

How to Take RSO

Because RSO is extremely potent, careful dosing is essential. Swallowed THC can take up to 2 hours to kick in, so don’t take more just because you don’t feel it yet.

Rick Simpson’s Original Protocol

This is the schedule Simpson promoted, shown for historical context only. It was never tested in clinical trials, and a gram a day of 60–90% THC oil is a very large THC dose.

• Start: Half a grain of rice-sized dose, 3x daily.
• Increase every 4 days.
• Target: 1 gram per day by week 4–5.
• Goal: 60 grams over 90 days.

Modern Approach

• Most adults in legal markets use far smaller amounts than the original protocol.
• Dispensary labels list milligrams of THC, so you can measure. Start low and wait before taking more.
• Medical-program patients should ask a clinician about dosing and drug interactions.

Methods of Use

• Oral ingestion (capsules or syringes): Slow onset, long-lasting effects.
• Sublingual tinctures: Held under the tongue.
• Topical: Applied to the skin.
• Edibles: Delayed but extended effects.

Side Effects & Safety

Common Side Effects

• Drowsiness
• Dizziness
• Dry mouth
• Anxiety/paranoia (if too much taken)
• Hunger (“the munchies”)

Who Should Avoid RSO

• Pregnant or breastfeeding individuals
• People with history of psychosis
• Those with THC restrictions (workplace drug testing)
• Anyone who needs to drive

Keep RSO locked away from children and pets; a small amount contains a lot of THC.

Where to Buy RSO

Licensed Dispensaries

• Safest and most reliable option.
• Look for lab-tested RSO with Certificates of Analysis (COAs) showing potency and residual-solvent results.

Online Sellers

• Many claim to sell RSO, but beware of scams and fake oils. High-THC RSO can’t legally ship across US state lines.
• Always request lab results before purchase.

Caregivers & Homemade

• Some registered caregivers provide RSO where state law allows it, but quality varies.

Tip: Search “RSO near me” or “where to buy RSO oil” in your state to find regulated options.

Legal Status of RSO

• USA: Legal only in states with medical or adult-use programs. Federally, adult-use marijuana remains Schedule I; since April 28, 2026, FDA-approved marijuana drug products and marijuana handled under a state medical-marijuana license are in Schedule III (Federal Register 2026-08176). High-THC RSO is not hemp.
• Canada: Legal for adults to buy cannabis extracts from provincially authorized retailers under the Cannabis Act.
• Europe: Mixed — legal in some countries, banned in others.
• Asia/Middle East: Mostly illegal.
• Latin America: Slowly expanding medical cannabis programs.

FAQs About RSO

Final Thoughts on RSO

RSO is one of the most potent and best-known cannabis extracts. If you’re thinking about trying it, the most important factors are:

• Start with very small doses.
• Buy only from trusted, lab-tested sources.
• Respect its potency.
• Talk to a clinician if you have a health condition.

RSO isn’t for everyone. Learn how full extract cannabis oil is made with online cannabis cooking and extraction courses from CTU, or study extraction in more depth in the Cannabis Extraction course.

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