THC oil is a cannabis extract with a high content of THC (tetrahydrocannabinol), the compound that causes the cannabis "high". It is made by extracting the resin from cannabis flowers and usually diluting it in a carrier oil. In the UK, THC is a Class B controlled drug, so THC oil is illegal unless it is a prescribed cannabis-based medicine. It is not the same as CBD oil.
Key facts
- What it is
- An extract of drug-type cannabis, rich in THC, often diluted in a carrier oil
- Main active compound
- Delta-9-THC, a partial agonist at the CB1 and CB2 cannabinoid receptors
- UK legal status
- As of October 2026, THC is a Class B drug under the Misuse of Drugs Act 1971. Cannabis-based products for medicinal use can be prescribed by specialist doctors (rescheduled in 2018).
- CBD products
- Pure CBD is not controlled. CBD products that contain controlled cannabinoids such as THC are controlled unless they meet the legal "exempt product" definition.
- Stability
- Heat, light and oxidation break THC down, mainly into CBN
What is THC oil?
THC oil is a concentrated extract of cannabis. Producers extract the resin from the flowers of THC-rich cannabis plants, usually with CO2 or ethanol, and then dilute the extract in a carrier oil or sell it as a thick concentrate. The result can contain many times more THC than the dried flowers it was made from.
Names cause a lot of confusion here. "Cannabis oil" is used for THC oil, for CBD oil and sometimes even for hemp seed oil, which contains almost no cannabinoids. Our guide to hemp oil vs CBD oil explains the difference.
What is THC?
Tetrahydrocannabinol (THC) is the main intoxicating compound in cannabis. It binds to the CB1 and CB2 receptors of the endocannabinoid system as a partial agonist, and its action on CB1 receptors in the brain is behind the high (Pertwee, 2008).
In the living plant there is very little THC. The plant makes THCA, an acid form that does not intoxicate. THCA turns into THC when it is heated, a step called decarboxylation. Producers of THC oil therefore heat the plant material or the extract. Our guide to how heat affects cannabinoids covers this step.
How is cannabis THC oil made?
Most THC oil is made in three steps:
- Extraction: a solvent, often supercritical CO2 or ethanol, dissolves the cannabinoids and terpenes out of the flowers. Read more about CO2 extraction and other extraction methods.
- Decarboxylation: heat turns THCA into THC.
- Dilution or refining: the extract is mixed into a carrier oil or refined further into a stronger concentrate.
What colour is THC oil?
THC oil can be pale gold, amber, dark brown or greenish. The colour depends mainly on how the extract was made and refined, not on how much THC it contains. Chlorophyll and other plant material make a crude extract dark green or brown, while a filtered or distilled extract is lighter and clearer. CBD oil can look exactly the same, so you can't judge THC content by colour. Only a laboratory test shows it.
What is high THC oil, and how is it different from CBD oil?
"High THC oil" simply means an extract from drug-type cannabis, bred for THC. CBD oil is made from hemp, which is bred to contain little THC and much more CBD. The two can look alike but have different legal status and different effects. Our article on CBD vs THC goes into more detail.
| THC oil | CBD oil | |
|---|---|---|
| Source plant | Drug-type cannabis | Hemp (low THC) |
| Main cannabinoid | THC | CBD |
| Intoxicating | Yes | No |
| UK legal status (October 2026) | Class B drug; only legal as a prescribed medicine | Legal if it meets UK rules on controlled cannabinoids |
| Spectrum types | Usually a whole-plant extract | Full spectrum, broad spectrum or isolate |
"Broad-spectrum" and "full-spectrum" are terms from CBD products: full-spectrum CBD oil keeps the plant's minor cannabinoids, including a small amount of THC, while broad-spectrum oil has the THC removed. See full spectrum vs broad spectrum vs isolate.
Is THC oil legal in the UK?
No, not for general sale or possession. According to Home Office guidance, cannabis and cannabinol derivatives, including THC, are Class B drugs under the Misuse of Drugs Act 1971. Two exceptions matter:
- Prescribed medicines: cannabis-based products for medicinal use were moved to Schedule 2 of the Misuse of Drugs Regulations 2001 in 2018. Specialist doctors can prescribe them.
- CBD products: pure CBD is not controlled. A CBD product that contains controlled cannabinoids is controlled unless it meets the "exempt product" definition in Regulation 2 of the Misuse of Drugs Regulations 2001.
For the rules on CBD in particular, read is CBD oil legal in the UK?
How is THC content tested?
Laboratories usually test cannabis products with gas chromatography (GC-FID), the method set by the European Commission for hemp. The sample is heated in the instrument, which turns THCA into THC. A 2022 study showed that this heat also breaks down a small share of the cannabinoids, which researchers must account for (García-Valverde et al., 2022). For the full picture, see how THC levels are tested.
How should cannabis oils be stored?
Cannabinoids are sensitive to heat, light and oxygen. In the 2022 study, heat degraded both CBD and THC, and THC broke down mainly into CBN (García-Valverde et al., 2022). Any cannabis extract keeps best in a closed, dark glass bottle, away from heat and sunlight. CBD that reacts with oxygen can form CBE (cannabielsoin).
From our production
We don't make or sell THC oil, or any product meant to intoxicate. That includes HHC and THCA products that turn into THC when heated. Our oils are CBD oils, and we print the THC content of every one to two decimal places.
— Robin Roy Krigslund-Hansen, co-founder and CEO
Frequently asked questions
What is THC oil?
THC oil is a cannabis extract with a high content of THC, the compound that causes the cannabis high. It is usually made by extracting the resin from cannabis flowers and diluting it in a carrier oil.
Is THC oil legal in the UK?
No, except as a prescribed medicine. THC is a Class B drug under the Misuse of Drugs Act 1971. Since 2018, specialist doctors can prescribe cannabis-based products for medicinal use.
What colour is THC oil?
It ranges from pale gold to dark brown or green, depending on how the extract was made and refined. Colour does not show THC content; only a laboratory test does.
Is THC oil the same as CBD oil?
No. THC oil is made from drug-type cannabis and is intoxicating. CBD oil is made from hemp, contains mainly CBD and does not cause a high.
Is cannabis oil the same as THC oil?
Not always. "Cannabis oil" is used for THC oil, for CBD oil and even for hemp seed oil. Check the label and the certificate of analysis to see which cannabinoids a product contains.
Does Formula Swiss sell THC oil?
No. We make CBD oils and don't sell THC oil or any other product meant to intoxicate.
Related guides
Formula Swiss CBD oils are sold as cosmetics for use on the skin. They are not food supplements or medicines and are not intended to diagnose, treat, cure or prevent any disease. This article is general information about the law and the science, not legal or medical advice.
Last reviewed:
Sources
- Home Office. Drug licensing factsheet: cannabis, CBD and other cannabinoids. GOV.UK, updated 3 October 2024.
- Pertwee RG. The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin. British Journal of Pharmacology 2008. doi:10.1038/sj.bjp.0707442
- García-Valverde MT, et al. Effect of temperature in the degradation of cannabinoids: from a brief residence in the gas chromatography inlet port to a longer period in thermal treatments. Frontiers in Chemistry 2022. doi:10.3389/fchem.2022.1038729
