THCA (tetrahydrocannabinolic acid) is the acid form of THC that cannabis makes in its resin glands, and it is not intoxicating in raw plant material. Heat strips off its carboxyl group and turns it into THC, a reaction called decarboxylation. This happens quickly when cannabis is heated and slowly during storage, so fresh cannabis holds mostly THCA.
Key facts
- Formula
- C₂₂H₃₀O₄. THC is C₂₁H₃₀O₂ (PubChem).
- Intoxicating?
- Not in raw form. In a receptor study THC bound CB1 about 62 times more strongly than THCA (McPartland et al., 2017).
- What turns it into THC
- Heat, and more slowly time in storage. THCA decarboxylates about twice as fast as CBDA or CBGA (Wang et al., 2016).
- Human research (as of October 2026)
- None of the studies cited here were done in people; they used cells, rats, shrews and mice.
- UK status (as of October 2026)
- Pure isolated THC-A is not controlled, but it degrades into controlled THC (Home Office).
- At Formula Swiss
- We don't sell THCA products. Our certificates report THC after full decarboxylation.
What is THCA and where does it come from?
Cannabis makes its cannabinoids as acids. The first one is cannabigerolic acid (CBGA), which plant enzymes turn into the acid forms of THC, CBD and CBC (Jastrząb et al., 2022). In drug-type cannabis most CBGA becomes THCA, which builds up in the trichomes, the resin glands on the flowers and leaves. In fibre hemp a different enzyme makes CBDA instead (Taura et al., 2007). The acid forms dominate in the living plant; THC itself is present only in small amounts until the plant material is dried or heated (Wang et al., 2016).
The same chemistry applies to CBD and its acid, explained in what is CBDA?, and to CBG, the neutral form of CBGA, in what is CBG?
What is the chemical structure of THCA?
THCA has the three-ring structure of THC with a pentyl side chain, plus one extra carboxylic acid group (COOH) on the aromatic ring. That group is the whole difference. Its molecular formula is C₂₂H₃₀O₄; when it loses the group as CO₂, what remains is THC, C₂₁H₃₀O₂ (PubChem). Strictly, the main form in cannabis is THCA-A; the UK Home Office also names a second acid precursor, THCA-B, and refers to both as "THC-A".
How does THCA turn into THC?
Decarboxylation removes the carboxyl group as CO₂. Heat drives it: in a kinetic study at 80 to 145 °C, THCA converted about twice as fast as CBDA or CBGA, and without side products (Wang et al., 2016). The reaction also runs at room temperature, only slower. In cannabis samples seized in Austria, storage at high temperature turned THCA into THC faster and more completely, while freezer storage changed the ratio little or not at all (Taschwer and Schmid, 2015).
This is why raw cannabis and heated cannabis act so differently, and why THCA matters for drug testing. See CBD, drug tests and driving.
What is the difference between THCA and THC?
| Point | THCA | THC | CBD |
|---|---|---|---|
| Formula | C₂₂H₃₀O₄ | C₂₁H₃₀O₂ | C₂₁H₃₀O₂ |
| Form | Acid, made by the plant | Neutral, formed by heat | Neutral, formed from CBDA by heat |
| Intoxicating | No, unless heated | Yes | No |
| CB1 receptor | Weak binding | About 62 times stronger binding than THCA | Low affinity |
| UK status | Pure isolate not controlled | Class B controlled drug | Not controlled |
CB1 data: McPartland et al. (2017) for THCA and THC, Pertwee (2008) for CBD. UK status: Home Office factsheet. For THC itself, read what is THC?
Does THCA get you high?
Not as long as it stays THCA. McPartland et al. (2017) measured only weak binding at the CB1 receptor and noted that part of even that weak signal probably came from THC formed in the sample, which is almost impossible to avoid. In rats, THCA did not cause the drop in body temperature or movement that CB1 activators cause (Rock et al., 2013). Once THCA is heated, for example by smoking or vaping, it becomes THC and is intoxicating. For the full list, see which cannabinoids are psychoactive.
What does research say about THCA?
Research on THCA is early and none of it is in people.
- Nausea models: in rats, THCA reduced nausea-induced gaping, and in shrews it reduced vomiting (Rock et al., 2013).
- PPARγ: THCA bound and activated the PPARγ receptor more potently than THC and protected nerve cells in cell and mouse models (Nadal et al., 2017).
- Instability: because THCA keeps turning into THC, it is hard to study on its own (McPartland et al., 2017). A review sets out the open questions (Moreno-Sanz, 2016).
These results do not show what THCA does in humans.
How do labs measure THCA?
Liquid chromatography keeps THCA intact, so it can report THCA and THC separately. Gas chromatography heats the sample, which turns THCA into THC, so it reports the two together unless the sample is derivatised first. Lab reports for cannabis products therefore often give "total THC", which counts THCA as the THC it can become.
Our oils are tested by gas chromatography with flame ionisation detection (GC-FID) in a laboratory in Switzerland. Our published certificates, for example report 260410_A01, state that the values are totals after complete decarboxylation. You can check them on our test results page, and our guide explains how THC is measured in hemp.
Is THCA legal?
The UK Home Office states that pure, isolated THC-A is not controlled under the Misuse of Drugs Act 1971, but that it readily degrades into THC, a Class B, Schedule 1 controlled cannabinoid. That statement covers the pure substance only. Whether THCA flowers, extracts or finished products are lawful depends on their THC content and on the product rules, and laws differ from country to country. For concentrated extracts of THC-rich cannabis, see THC oil and the law.
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. We test every batch in Switzerland, and I sign every certificate of analysis myself.
— Robin Roy Krigslund-Hansen, co-founder and CEO
Our oils are listed in the CBD oil collection, each with the THC value of its batch.
Frequently asked questions
What is THCA?
THCA, or tetrahydrocannabinolic acid, is the acid form of THC that cannabis makes in its resin glands. It is not intoxicating in raw plant material, but heat turns it into THC.
What is the chemical structure of THCA?
THCA has the same three-ring structure and pentyl side chain as THC, plus a carboxylic acid group (COOH). Its formula is C22H30O4. When it loses that group as CO2, it becomes THC, C21H30O2.
Does THCA turn into THC over time?
Yes. Heat converts THCA into THC quickly, and the reaction also runs slowly during storage. In seized cannabis stored at high temperatures, THCA broke down to THC faster and more completely than in samples kept cold (Taschwer and Schmid, 2015).
Does THCA get you high?
Not in its raw form. In a receptor study THC bound the CB1 receptor about 62 times more strongly than THCA. Once THCA is heated, for example by smoking or vaping, it becomes THC, which is intoxicating.
How is THCA measured?
Liquid chromatography keeps THCA intact, so it can report THCA and THC separately. Gas chromatography heats the sample and turns THCA into THC, so lab reports often give total THC, which counts THCA as the THC it can become.
Is THCA legal in the UK?
The UK Home Office states that pure isolated THC-A is not controlled under the Misuse of Drugs Act 1971, but that it readily degrades into THC, which is a Class B controlled drug. That does not make THCA flowers or extracts lawful; their THC content and the product rules still apply.
Related guides
This article is general information about cannabis science and is not medical advice. Formula Swiss oils are sold as cosmetics for use on the skin, and our pet oils are for external use. Read our full disclaimer.
Last reviewed:
Sources
- PubChem. delta9-Tetrahydrocannabinolic acid (CID 98523) and Tetrahydrocannabinol (CID 16078). National Library of Medicine
- McPartland JM, et al. Affinity and efficacy studies of tetrahydrocannabinolic acid A at cannabinoid receptor types one and two. Cannabis and Cannabinoid Research 2017;2(1):87-95. PMID 28861508
- Wang M, et al. Decarboxylation study of acidic cannabinoids. Cannabis and Cannabinoid Research 2016;1(1):262-271. PMID 28861498
- Taschwer M, Schmid MG. Determination of the relative percentage distribution of THCA and Δ9-THC in herbal cannabis seized in Austria. Forensic Science International 2015;254:167-171. PMID 26247127
- Jastrząb A, Jarocka-Karpowicz I, Skrzydlewska E. The origin and biomedical relevance of cannabigerol. International Journal of Molecular Sciences 2022;23(14):7929.
- Taura F, et al. Cannabidiolic-acid synthase, the chemotype-determining enzyme in the fiber-type Cannabis sativa. FEBS Letters 2007;581(16):2929-2934. PMID 17544411
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- Rock EM, et al. Tetrahydrocannabinolic acid reduces nausea-induced conditioned gaping in rats and vomiting in Suncus murinus. British Journal of Pharmacology 2013;170(3):641-648. PMID 23889598
- Nadal X, et al. Tetrahydrocannabinolic acid is a potent PPARγ agonist with neuroprotective activity. British Journal of Pharmacology 2017;174(23):4263-4276. PMID 28853159
- Moreno-Sanz G. Can you pass the acid test? Critical review and novel therapeutic perspectives of Δ9-tetrahydrocannabinolic acid A. Cannabis and Cannabinoid Research 2016;1(1):124-130. PMID 28861488
- Home Office. Drug licensing factsheet: cannabis, CBD and other cannabinoids. GOV.UK
