CBD decarboxylation: what temperature, and for how long?
Decarboxylation is the reaction that turns CBDA, the form hemp actually produces, into CBD: heat removes a carboxyl group from the molecule, which escapes as CO₂. Published measurements place the effective range between 110 and 140 °C. At 110 °C, converting 95% of the CBDA in an extract takes about an hour. Below 100 °C the reaction remains incomplete, and from 160 °C the CBD content begins to drop.
Key takeaways
- Hemp flowers hold mostly CBDA, and CBD appears in quantity only once they are heated.
- In an extract at 110 °C, half the CBDA converts in 14 minutes and 95% in about 60 minutes.
- Boiling water converts little: 6.6% of THCA in 15 minutes, with CBDA reacting at about half that speed.
- Measured CBD and THC levels go down above 160 °C.
- Foods containing CBD have been off sale in France since May 2026, so this article describes a chemical reaction and gives no recipe.
Decarboxylation: definition and total CBD
Hemp produces almost no CBD as such. Its glands make cannabidiolic acid, CBDA, a molecule with an extra carboxyl group (COOH). Heat breaks that group off as CO₂ and leaves CBD behind. THCA becomes THC and CBGA becomes CBG by the same reaction.
In the process, the molecule loses about 12% of its mass, which is why the CBD and CBDA lines of a certificate of analysis cannot just be added together. The standard formula is total CBD = CBD + 0.877 × CBDA. A flower with 0.5% CBD and 8% CBDA, for example, yields at most 7.5% CBD once fully heated. Our guide to reading a certificate of analysis goes through this calculation line by line.
No oven is needed for the reaction to start. It progresses slowly during drying and storage, and almost instantly in a vaporiser or when the plant burns. In a home preparation, the aim is to complete it while keeping what it produces intact.
Temperature and time: what the studies measured
The reference work is a kinetics study published in 2016 in Cannabis and Cannabinoid Research. Wang and colleagues heated flower extracts in vials, in a vacuum oven with no air or light, at temperatures from 80 to 145 °C, and measured the reaction rate at each one. CBDA converted at about half the speed of THCA. We used their rates to calculate the share converted after 30 and 60 minutes.
| Temperature | CBDA converted in 30 min | CBDA converted in 60 min | Time to convert half |
|---|---|---|---|
| 80 °C | 8.6% | 16.5% | 231 min |
| 95 °C | 38.5% | 62.2% | 43 min |
| 110 °C | 77.6% | 95.0% | 14 min |
Keep two limits in mind. These figures come from an extract under vacuum, and crumbled flower in a kitchen oven behaves differently. The reaction also has side products: over the heating, the combined CBDA + CBD in the extract dropped by 18% at 110 °C and by 25% at 130 °C, as part of the CBDA turned into other compounds. Longer heating does not always give more CBD.
Two other teams add to this. An Italian team of pharmacists compared several protocols for oils in 2019, and pre-heating at 140 °C for 30 minutes worked better than pre-heating at 115 °C for 40 minutes. They insist on layer thickness so the heat spreads evenly: 5 mm of material at most, ideally 1 to 2 mm. In 2021, a study in the Journal of Cannabis Research heated hemp under pressure for 6 minutes. CBD content was highest at 140 °C and fell at 160 °C, where CBD and THC both showed signs of degradation.
Oven, fat, water, vaporiser: the methods compared
Based on the measurements cited above, the table shows what each method can achieve.
| Method | Actual temperature | What the measurements show | Weak point |
|---|---|---|---|
| Oven, material spread out | 110 to 140 °C | Near-complete conversion in 30 to 60 min | Inaccurate thermostat, terpenes lost |
| Fat in a water bath | 100 °C at most | At best 62% in an hour at 95 °C | Incomplete without pre-heating |
| Boiling water, tea | 100 °C | 6.6% of THCA converted in 15 min | Cannabinoids barely dissolve in water |
| Vaporiser set to 210 °C | 210 °C | At least 94.6% of acids converted | Inhalation only |
Among home methods, only the oven reaches the effective range. Fat in a water bath stays at 100 °C or below. Since CBD dissolves in fat, extraction works well, yet only part of the CBDA gets converted, which is why the Italian protocol pre-heats the material in an oven before the oil bath. Water does less still: in the 2007 study on cannabis tea, only 6.6% of the THCA added to boiling water had become THC after 15 minutes. CBDA reacts more slowly, so a tea converts even less of it.
A vaporiser needs no preparation at all. An in vitro study in PLOS One tested five devices at 210 °C in 2016, and the electric models decarboxylated at least 94.6% of the acids. These measurements are detailed in our guide to vaporisation temperature.
The mistakes that skew the result
The first mistake is to rely on the thermostat. The temperature at the tray can differ from the dial setting, and an oven thermometer placed next to the material shows you the real figure. According to the table, fifteen degrees separate 62% from 95% of CBDA converted in an hour.
Next comes layer thickness. The Italian team found that a layer over 5 mm thick heats poorly in the middle. Crumble the flower, stop short of powder, and spread it in a single layer.
Turning up the heat to save time is the third. From 160 °C, measured CBD losses outweigh what you gain in speed. Terpenes are more volatile and evaporate as the material heats, so its smell changes and becomes more toasted.
The last concerns the starting material. A flower that is old or was stored somewhere warm has already begun to decarboxylate, and a certificate of analysis dating from harvest no longer describes it exactly. When you choose CBD flowers, check the analysis date as carefully as the percentage shown.
What French law says
Whatever the chemistry, a product's legal status stays the same. In France, hemp flowers may be sold if they contain no more than 0.30% Δ⁹-THC and are not presented as food. For products meant to be swallowed, the Ministry of Agriculture restated on 20 May 2026 that foods containing CBD are not authorised and must be withdrawn from the market. They have no approval under the EU novel food regulation. What is still on sale is set out in our overview of CBD regulation in 2026.
People often forget that decarboxylation turns THCA into THC as well. A compliant flower holds traces of both, and heating increases its free THC content.
Frequently asked questions
The chemical reaction by which CBDA, the form the plant makes, becomes CBD. Heat takes a carboxyl group off the molecule, and it escapes as CO₂. THCA becomes THC the same way.
The effective range in the studies is 110 to 140 °C. An extract at 110 °C has 95% of its CBDA converted in about 60 minutes, and a protocol at 140 °C for 30 minutes also proved effective. Under 100 °C, the reaction does not finish.
No. According to a 2016 study of five devices, an electric vaporiser set to 210 °C converts at least 94.6% of the acids as you inhale.
Very little. In the 2007 study, 15 minutes of boiling converted only 6.6% of the THCA, and CBDA reacts at about half the speed of THCA. In France, infusions made from flowering tops have also been off sale since May 2026.
The flower has not been heated yet. Its potential is given by CBD + 0.877 × CBDA, a formula that allows for the mass lost with the CO₂.
Written by the Phytogrammes team
Each journal article draws on cited primary sources: ANSM, EFSA, EUR-Lex and peer-reviewed publications. Product profiles are distinguished from documented laboratory results. Our approach.
Article published on . CBD is not a medicine.