Tetrahydrocannabutol (Δ9-THCB) is the butyl homologue of THC: the same molecule with a four-carbon side chain instead of five. Italian researchers isolated it from a medical cannabis variety in a study published in 2020. In lab tests it bound the CB1 receptor about as strongly as THC. It has not been studied in people, and in the UK it is a Class B drug.
Key facts
- What it is
- The butyl (4-carbon) homologue of Δ9-THC
- Discovery
- Isolated from the FM2 medical cannabis variety, together with its CBD counterpart CBDB (published 2020)
- CB1 receptor (lab)
- Affinity comparable to THC (Ki 15 nM)
- In mice
- Partial CB1 agonist activity in the tetrad test
- UK legal status
- Class B: 3-alkyl homologues of THC count as cannabinol derivatives (as of October 2026)
What is tetrahydrocannabutol?
THC has a five-carbon (pentyl) side chain. Change the length of that chain and you get a homologue. THCV has three carbons, tetrahydrocannabutol (THCB) four, THCH six and THCP seven.
The chain length matters because it affects how the molecule sits in cannabinoid receptors. That is why researchers study each homologue separately rather than assuming it behaves like THC.
How was THCB discovered?
Italian researchers isolated Δ9-THCB and its CBD counterpart, cannabidibutol (CBDB), from the flowers of the FM2 medical cannabis variety. They confirmed the structures with NMR, mass spectrometry and other methods, and by comparing them with versions made by synthesis (Linciano et al., 2020).
The same group also described the heptyl homologue THCP (Citti et al., 2019). These finds showed that cannabis makes more THC homologues than once thought.
Does THCB get you high?
There are no human studies, but the lab data point that way. THCB bound the human CB1 receptor (Ki = 15 nM) and the CB2 receptor (Ki = 51 nM) with an affinity comparable to THC. In the mouse tetrad test, a standard screen for THC-like effects, it showed partial agonist activity at CB1 (Linciano et al., 2020).
The same study also ran a formalin pain test in mice. That is early animal research and says nothing about effects in people.
THCB vs THC vs THCV: how do they compare?
| Feature | THCV | THCB | Δ9-THC |
|---|---|---|---|
| Side chain | 3 carbons (propyl) | 4 carbons (butyl) | 5 carbons (pentyl) |
| Found in cannabis | Yes, as a minor cannabinoid | Yes, isolated from FM2 (2020) | Main intoxicating cannabinoid |
| CB1 binding | Not covered here | Comparable to THC | Reference |
| Sold in synthetic products | Yes | Yes | Yes |
| UK status | Class B | Class B | Class B |
Sources for the table: Linciano et al., 2020; Tanaka and Kikura-Hanajiri, 2024; Home Office, 2024; Misuse of Drugs Act 1971, Schedule 2. Read more in What is THCV?
Is THCB sold in products?
Yes, in unregulated markets. A Japanese analysis of oil products sold online in 2022 and 2023 found Δ8- and Δ9-THCB, along with other THC homologues and synthesis by-products (Tanaka and Kikura-Hanajiri, 2024). Forensic laboratories have since added THCB to their blood and urine tests, noting that human pharmacological data for these homologues are lacking (Muir et al., 2025).
THCB is broken down by liver enzymes into hydroxylated and carboxylated metabolites similar to those of THC (James et al., 2026). Read our guide on drug tests and driving.
Is tetrahydrocannabutol legal in the UK?
No. The Misuse of Drugs Act 1971 defines cannabinol derivatives as "tetrahydro derivatives of cannabinol and 3-alkyl homologues of cannabinol or of its tetrahydro derivatives", and lists them as Class B drugs. THCB is a 3-alkyl homologue of THC. The Home Office confirms that THC and other cannabinol derivatives are Class B, while pure CBD is not controlled (Home Office, 2024).
From our production
We don't sell HHC or any other cannabinoid that intoxicates, and we don't sell THCA products that turn into THC when heated.
— Robin Roy Krigslund-Hansen, co-founder and CEO
Frequently asked questions
What is tetrahydrocannabutol (THCB)?
Tetrahydrocannabutol is a THC homologue with a four-carbon side chain instead of five. It was isolated from the FM2 medical cannabis variety and described in 2020.
Is THCB stronger than THC?
Not on current evidence. In lab tests it bound the CB1 receptor with an affinity comparable to THC, and in mice it acted as a partial CB1 agonist. It has not been tested in people.
Is delta-9 THCB natural?
It occurs naturally in at least one cannabis variety. THCB found in products sold online is typically made by synthesis, often alongside by-products.
Is THCB legal in the UK?
No. As a 3-alkyl homologue of THC, it is a cannabinol derivative under the Misuse of Drugs Act 1971 and a Class B drug.
Will THCB show up on a drug test?
It can. Forensic laboratories have validated methods to detect THCB in blood and urine, and it forms metabolites similar to those of THC.
Related guides
This article summarises published research. It is not medical advice. 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.
Last reviewed:
Sources
- Linciano P, Citti C, Luongo L, et al. Isolation of a high-affinity cannabinoid for the human CB1 receptor from a medicinal Cannabis sativa variety: Δ9-tetrahydrocannabutol, the butyl homologue of Δ9-tetrahydrocannabinol. J Nat Prod 2020;83(1):88–98. doi:10.1021/acs.jnatprod.9b00876
- Citti C, Linciano P, Russo F, et al. A novel phytocannabinoid isolated from Cannabis sativa L. with an in vivo cannabimimetic activity higher than Δ9-tetrahydrocannabinol: Δ9-tetrahydrocannabiphorol. Sci Rep 2019;9(1):20335. doi:10.1038/s41598-019-56785-1
- Tanaka R, Kikura-Hanajiri R. Identification of Δ8-tetrahydrocannabinol (THC) and Δ9-THC analogs, with different lengths of alkyl chain at C-3 position, in oil products distributed on the internet [in Japanese]. Yakugaku Zasshi 2024;144(8):823–837. doi:10.1248/yakushi.24-00029
- Muir LS, Doumit SE, Seither JZ, et al. Comprehensive LC-MS-MS analysis of THC isomers, analogs, homologs, and metabolites in blood and urine. J Anal Toxicol 2025;49(5):322–331. doi:10.1093/jat/bkaf023
- James KM, Poklis JL, Karschner EL, Dempsey SK, Peace MR. Delta-9-tetrahydrocannabutol, delta-9-tetrahydrocannabihexol, and delta-9-tetrahydrocannabiphorol: the impact of varying alkyl chain length on delta-9-tetrahydrocannabinol analog metabolism. J Anal Toxicol 2026;50(8):bkag045. doi:10.1093/jat/bkag045
- Home Office. Drug licensing factsheet: cannabis, CBD and other cannabinoids (updated 3 October 2024). gov.uk
- Misuse of Drugs Act 1971, Schedule 2. legislation.gov.uk
