THCA (THC acid): the raw form of THC, heat and French law

THCA belongs to the acidic cannabinoids. The plant first builds cannabigerolic acid (CBGA), which an enzyme, THCA synthase, converts into THCA. CBD follows the same pattern, with CBDA as its plant form. THCA carries a carboxyl group (COOH), a small chemical group that THC has lost.

A review published in 2016 in Cannabis and Cannabinoid Research reports that THCA accumulates in the glandular trichomes of flowers and leaves, where it represents up to 90% of total THC. The review adds that THCA, unlike THC, has no psychoactive effects in humans. Studies disagree on how it binds to the CB1 receptor, THC's main target in the brain. In storage it slowly converts into THC, which can then break down into CBN.

These resin glands are described in our article on trichomes, and the effect of light and heat during storage in our guide to storing flowers. Most research on the effects of THCA itself is still done on cells and animals.

The two molecules differ by a single carboxyl group: the plant makes THCA, then heat or time turns it into THC. The first has no psychoactive effect as it stands, the second has one. French texts handle them separately, but the official measurement method brings them together in a single result.

The molar masses published by PubChem for THCA and THC explain the factor used in calculations. During decarboxylation, the carboxyl group leaves as carbon dioxide, and 1 g of THCA can yield at most 0.877 g of THC, the ratio of 314.5 to 358.5. In practice the conversion is incomplete and part of the THC formed breaks down, so the real yield is lower.

Decarboxylation is the loss of that carboxyl group under heat, released as carbon dioxide. Burning, vaporising and cooking all set it off. Along the way, the molecule sheds about 12% of its mass, which is where the 0.877 factor in calculations comes from.

A 2016 study tracked the reaction in a vacuum oven, between 80 and 145 °C. At 80, 95 and 110 °C, the authors determined a reaction rate, from which we derived the half-life, the time needed to convert half of the THCA. For the higher temperatures, they recorded the point at which THCA had nearly vanished.

That explains why a raw flower lacks the effect of one that is smoked or heated. The methods and their limits are covered in our guide to decarboxylation.

Not in compliant hemp. On 22 May 2024, the French medicines agency (ANSM) decided to classify several cannabinoids as controlled drugs from 3 June 2024. The list covered H4CBD and H2CBD and a whole family of derivatives, among them HHC, already controlled since 13 June 2023, THCP and, because of its chemical structure, THCA. The target was products sold online and in shops that imitate the effects of THC.

The text of the decision of 22 May 2024, published on 24 May and in force ten days later, covers any substance derived from the benzo[c]chromene nucleus, including when it carries a carboxyl function at position 2 or 4. That describes THCA, whose chemical name places this group at position 2.

By 3 June, the agency had already amended the classification. Its decision of 3 June 2024, published on 4 June, exempts substances that industrial hemp products may contain at very low concentrations: CBNA, THCV and THCVA, the latter two as long as their content does not exceed 0.3%, and THCA "subject to compliance with the content set in article 1 of the order of 30 December 2021". THCA in hemp whose Δ⁹-THC content is 0.30% at most is therefore not a controlled drug.

H4CBD and THCP are still banned: our article on the H4CBD ban traces that classification, and our guide to THCP gives the details for that molecule. The history of HHC is told in our article on HHC. A product rich in THCA that exceeds the THC threshold gets no exemption either.

On a reading of the texts, because the content that decides the status of hemp is determined, in France as in the European Union, by gas chromatography: the sample is heated, and THCA turns almost entirely into THC before it is counted. The order does not name THCA; it is the method the order prescribes that brings THCA into the result.

The threshold applies to Δ⁹-THC. The French order of 30 December 2021 authorises varieties listed in the EU or French variety catalogues whose Δ⁹-THC content is 0.30% at most, and applies the same ceiling to hemp extracts and the products that contain them. Its annex prescribes measurement by gas chromatography, under a procedure A or a procedure B, with a tolerance of 0.03 point.

The Union method has the same procedures A and B. Regulation (EU) 2021/2115 (Article 4(4)) admits hemp areas to farm aid only if the varieties used have a THC content not exceeding 0.3%, and Annex I of Delegated Regulation (EU) 2022/126 sets out the method: solvent extraction, a chromatograph fitted with a flame ionisation detector, a 300 °C injector given as an example, a result expressed to two decimals in grams of THC per 100 g of dried sample, and a tolerance of 0.03 g per 100 g.

At those temperatures, THCA decarboxylates inside the instrument. A study published in 2022 in Frontiers in Chemistry injected standard solutions into an injector set between 250 and 350 °C, and nearly all THCA converted to its neutral form. The same study puts figures on the method's limits. At 300 °C, the temperature of the official example, CBD loses up to 20% of its concentration, partly to Δ⁹-THC and CBN, and Δ⁹-THC itself loses 17.2%, mostly to CBN. The official figure therefore comes close to total THC without being equal to it, and a CBD-rich flower can see part of its CBD come out as Δ⁹-THC.

The US regulator describes the same mechanism in its own words. According to 7 CFR 990.1, gas chromatography, because it heats the sample, converts THCA into THC and gives a "post-decarboxylation" value; liquid chromatography keeps THCA intact and requires the calculation Δ⁹-THC + 0.877 × THCA.

Liquid chromatography (HPLC), used for most certificates of analysis, leaves the sample unheated and reports the two forms separately. The standard calculation shows where a product stands: total THC = Δ⁹-THC + 0.877 × THCA. Two fictional flowers illustrate the stakes.

Flower B has a low Δ⁹-THC, yet the official measurement would place it above the threshold. Once heated, a flower sold as "THCA-rich" becomes a THC-rich flower.

Food law follows the same logic. For hemp seeds and their products, Regulation (EU) 2023/915, which repealed Regulation No 1881/2006, sets the maximum level on the sum Δ⁹-THC + 0.877 × Δ⁹-THCA. Those limits come from Regulation (EU) 2022/1393, which amended the repealed text on the grounds that THCA can turn into THC during processing.

Where the threshold comes from is explained in our article on the legal THC level, and our guide to reading a certificate of analysis shows where both lines appear.

On a reading of the texts, no. A flower sold for its high THCA content goes far beyond 0.30% as soon as it is measured by the official method, which heats the sample and counts that THCA together with the THC. And the exemption the ANSM decided on 3 June 2024 only covers THCA in hemp that respects this ceiling.

Take a fictional label that reads "Δ⁹-THC 0.15% · THCA 18%". The calculation goes as follows.

A label of this kind can mislead in three ways.

• It highlights the Δ⁹-THC line, measured without heating, and moves THCA further down, when it does not leave it out.
• A claim such as "THC < 0.3%" or "EU compliant" then refers only to that Δ⁹-THC, whereas the official method in effect adds the THCA that heat converts.
• The "legal in the United States" argument points to a US definition that never applied in France, as the next section explains.

The same calculation applies to the other products sold under the THCA label: resin or hash, vape cartridges, "diamonds" or crystals. The more concentrated the product, the wider the gap. Under the official method, an isolate close to 100% THCA would come out at up to about 88% THC, since 1 g of THCA yields at most 0.877 g. Our guide to wax and concentrates shows that a concentrate also multiplies the THC of the starting plant.

Some sellers also promote raw THCA, in juice or smoothies. It is admittedly not psychoactive as it stands, but, on a reading of the texts, the status of a product depends on its THC content measured by the official method, not on the way it would be consumed. A product meant to be swallowed also falls under the novel food rules, set out in our article on legal CBD in 2026.

Taken together, these texts lead to the following reading: a flower or a resin whose content measured according to the annex of the order exceeds 0.30% (0.33% with the tolerance) benefits neither from the authorisation of the order of 30 December 2021 nor from the THCA exemption decided on 3 June 2024. This reading is not legal advice: for a specific case, consult a lawyer.

Because US federal law still defines hemp by its delta-9-THC content alone. Since the Farm Bill of 20 December 2018, 7 U.S.C. 1639o defines hemp as the plant with no more than 0.3% delta-9-THC on a dry weight basis: the trade in "THCA flowers" relies on this text, which names delta-9-THC only, even though the US Department of Agriculture already counts THCA when it checks crops (7 CFR 990.1).

Congress voted to close that gap with Public Law 119-37 of 12 November 2025 (section 781): 365 days after enactment, the 0.3% threshold was to apply to total tetrahydrocannabinols, "including tetrahydrocannabinolic acid", and finished products with more than 0.4 mg of total THC per container were to fall outside the definition. Public Law 119-103 of 2 September 2026 (section 2019), however, limits that reform, until 11 December 2026, to cannabinoids the plant cannot produce naturally: read this way, the rule only reaches THCA at the end of that period.

None of this timetable changes anything in France, which applies its own list of controlled drugs and its own measurement method. Edible products from the United States are covered in our articles on ingested THC and on THC gummies. Situation checked on 28 October 2026.

On a reading of the texts, a product whose THC content exceeds the ceiling falls under the regime of cannabis as a controlled drug. Article L3421-1 of the French Public Health Code, in its version in force since 20 August 2026, punishes the illicit use of a controlled drug with one year in prison and a fine of 3,750 €. Prosecution can be closed by a fixed criminal fine of 500 €, reduced to 400 € if paid within 15 days and raised to 1,000 € if not paid within 45 days, as Service-public explains.

At the wheel, no threshold applies. Article L235-1 of the French Highway Code punishes driving after drug use, established by a saliva or blood analysis, with 3 years in prison and a fine of 9,000 €, and with 5 years and 15,000 € if blood alcohol is also over the legal limit; the licence can be suspended for up to 5 years. In a judgment of 21 June 2023 (No. 22-85.530), the Cour de cassation ruled that the authorisation to sell some cannabis derivatives with no more than 0.30% Δ⁹-THC "has no bearing" on this offence, which is made out "whatever the dose absorbed". Heating THCA, by smoking or vaporising it, produces THC, the substance these tests look for.

Detection windows and the course of a roadside check are covered in our guide to the saliva test and in our article on CBD and driving. For any question about these products, Drogues Info Service answers on 0 800 23 13 13, free of charge and anonymously. In an emergency, call 15 or 112; deaf or hard-of-hearing people can reach 114 by text message, app or internet.

In France, the status of THCA rests on two ANSM decisions signed twelve days apart in 2024, the second of which refers to an order of 2021. In the United States, the timetable is still moving, and the next deadline falls on 11 December 2026. Status checked on 28 October 2026.

The sources were consulted between 20 and 28 October 2026; the dates are those of the publications or of the versions cited.

• Moreno-Sanz, review on tetrahydrocannabinolic acid, Cannabis and Cannabinoid Research: 2016.
• Wang et al., study of the decarboxylation of acidic cannabinoids, Cannabis and Cannabinoid Research: 2016.
• García-Valverde et al., Frontiers in Chemistry, vol. 10, article 1038729: 1 November 2022.
• PubChem, entries for THC (CID 16078) and THCA (CID 98523): living database.
• ANSM, decision of 22 May 2024, published on 24 May 2024; decision of 3 June 2024, published on 4 June 2024; news item on the newly classified cannabinoids: published on 24 May 2024, updated on 11 March 2025.
• Order of 30 December 2021 implementing Article R. 5132-86 of the French Public Health Code, published in the Journal officiel of 31 December 2021: consolidated version.
• Regulation (EU) 2021/2115 of 2 December 2021, Article 4; Delegated Regulation (EU) 2022/126 of 7 December 2021, Annex I, published on 31 January 2022.
• Regulation (EU) 2022/1393 of 11 August 2022; Regulation (EU) 2023/915 of 25 April 2023, Annex I, point 2.6.
• United States: 7 U.S.C. 1639o, from Public Law 115-334 of 20 December 2018; Public Law 119-37 of 12 November 2025, section 781; Public Law 119-103 of 2 September 2026, section 2019; 7 CFR 990.1: online version.
• French Public Health Code, Article L3421-1, and Highway Code, Article L235-1: versions in force since 20 August 2026. Service-public, "Que risque-t-on pour usage de drogues ?": page updated on 21 August 2026.
• Cour de cassation, criminal chamber, 21 June 2023, No. 22-85.530.