CBD e-liquid: 300 mg does not mean 300 mg/ml
The big number on a CBD e-liquid bottle is the total amount inside, to be divided by the volume to get mg/ml. A 10 ml bottle labelled 300 mg holds 30 mg per millilitre; in 30 ml, the same total gives only 10. Compare products per millilitre, then check the composition and the batch certificate of analysis.
Key takeaways
- mg/ml = total amount in mg ÷ bottle volume in ml.
- The single human measurement published, from a 1986 study, gives 31% of CBD absorbed by smoking.
- An e-liquid is made of propylene glycol and vegetable glycerine, and oil has no place in it.
- French law treats a CBD e-liquid as a vaping product, which may not be sold to under-18s.
- The ANSM found "CBD" e-liquids that contained HHC, H4-CBD or synthetic cannabinoids.
The calculation: divide the total by the volume
Divide the total amount of CBD by the bottle volume and you have the concentration. A 10 ml bottle labelled 300 mg holds 30 mg per millilitre, and the same bottle labelled 1,000 mg holds 100. A 30 ml bottle labelled 300 mg holds only 10.
This is the most frequent mistake, because labels highlight the bottle total and rarely the concentration. Two products sold as "300 mg" can differ by a factor of three.
| Stated amount | 10 ml bottle | 30 ml bottle |
|---|---|---|
| 100 mg | 10 mg/ml | 3.3 mg/ml |
| 300 mg | 30 mg/ml | 10 mg/ml |
| 500 mg | 50 mg/ml | 16.7 mg/ml |
| 1,000 mg | 100 mg/ml | 33.3 mg/ml |
The calculation also works the other way. If you vape 1 ml a day of a liquid at 30 mg/ml, you vaporise 30 mg of CBD. You do not absorb all of it: part of the vapour is exhaled, and part settles in the mouth. The hardware also changes how much liquid each puff vaporises, as our article on coil resistance and power explains.
How much CBD actually reaches the body
Human data are thin. A systematic review published in 2018 in Frontiers in Pharmacology collected the studies on the pharmacokinetics of cannabidiol in humans. It reports an average bioavailability of 31% by smoking, drawn from a single 1986 study. Nobody has measured the absolute bioavailability of swallowed CBD in humans, so the figures often quoted to compare vaping and swallowing have no human data behind them.
No authority has set a reference dose for inhaled CBD; the only official value concerns ingestion. On 9 February 2026, EFSA set a provisional safe level of 0.0275 mg per kilo per day, about 2 mg for a 70 kg adult. It applies to CBD of at least 98% purity taken as a food supplement. The agency could not establish that CBD is safe under 25, during pregnancy or breastfeeding, or for people on medication.
What an e-liquid contains, and what it must never contain
An e-liquid rests on two solvents, propylene glycol (PG) and vegetable glycerine (VG), whose ratio sets the viscosity and the behaviour under heat. CBD is added, often with flavourings. It may come from an isolate, which is CBD alone, or from an extract that keeps other plant compounds. A full-spectrum extract can bring traces of THC, which matters if you drive; our article on full spectrum versus isolate explains the differences. A CBD e-liquid can also contain nicotine, and the label must then say so.
Oil does not belong in this mix. The reference case is the US outbreak of vaping-associated lung injury (EVALI). On 18 February 2020, the Centers for Disease Control and Prevention counted 2,807 hospitalised cases or deaths, including 68 deaths. Vitamin E acetate, an oily substance added to thicken THC liquids, was found in the lung fluid of 48 patients out of 51.
A distorted version of this story often circulates. The first analysis report, published in November 2019, covered 29 bronchoalveolar lavage samples, and vitamin E acetate was present in all 29. Plant oils, medium-chain triglyceride oil and petroleum distillates all stayed below detection limits. The agent implicated is vitamin E acetate; coconut oil is not. The principle drawn from the case still holds: a fatty substance has no place in an inhaled aerosol.
Heat raises another problem. A study published in 2021 in Scientific Reports shows that, with oxygen present, PG and glycerine break down from 133 to 175 °C, forming formaldehyde, acetaldehyde, formic acid and acrylic acid. This starts well before any burnt taste appears. Pushing a coil beyond its range, or pulling on a dry wick, carries a real risk.
Heat can also convert CBD itself. A Hungarian team heated pure CBD between 250 and 500 °C: 25 to 52% was transformed, mostly into Δ⁹-THC. A German team then checked what happens in an e-cigarette, vaping two CBD e-liquids with two devices, one of them pushed to 0.2 ohm and 200 watts. It found no rise in THC in the condensed liquids. Under realistic use, the conversion does not appear to happen to any notable extent.
The French legal framework
French law treats a CBD e-liquid as a vaping product. Article L3513-1 of the Public Health Code covers liquids "containing nicotine where applicable", which includes those with none. Two rules follow. Article L3513-5 bans sale to under-18s and requires sellers to ask for proof of age. Article L3513-4 bans direct or indirect advertising for these products. Our article on the legal age for CBD compares formats.
Law no. 2025-175 of 24 February 2025 bans prefilled, non-refillable vaping devices. Cartridges are expressly excluded from the ban, and refill bottles fall outside it. Our article on the disposable puff ban covers the measure in detail.
The Δ⁹-THC content follows the general hemp rules: paragraph III of article 1 of the decree of 30 December 2021 caps hemp extracts, and the products containing them, at 0.30%, e-liquids included.
An e-liquid is not a food, so the Ministry of Agriculture notice of 20 May 2026, which calls for the withdrawal of CBD foods and supplements, does not cover it. It is legal because it sits outside the food category; it has no authorisation of its own.
Why the lab test matters more than the label
French authorities have been explicit about this format. In a notice of 19 June 2025, the ANSM reported several hundred poisonings since early 2024 involving products presented as containing CBD, with e-liquids among the formats named. Tests found THC above the legal threshold, or HHC, HHC-O, H4-CBD, H2-CBD and MDMB-PINACA, a synthetic cannabinoid. The same notice cites a 2023 study in which 8 products out of 10 displayed a CBD content that differed from the measured one.
What is printed on the bottle proves nothing on its own; a batch certificate of analysis is the only answer. It should state the CBD content, in mg/ml or mg per bottle, a Δ⁹-THC content of 0.30% or less, and ideally a screen for semi-synthetic cannabinoids. Check that its batch number matches the bottle. Our guide to reading a certificate of analysis takes each line in turn.
CBD is not a medicine. Vaping carries risks, with or without nicotine.
Frequently asked questions
Thirty milligrams per millilitre. The stated amount covers the whole bottle, and dividing it by the volume gives the concentration. In a 30 ml bottle, the same 300 mg comes to only 10 mg per millilitre.
No. Oil has no place in an inhaled aerosol. The US outbreak of vaping-associated lung injury, with 2,807 hospitalised cases or deaths as of 18 February 2020, was strongly linked to vitamin E acetate, an oily substance added to THC liquids.
Yes. They are vaping products, which may not be sold to minors, and their Δ⁹-THC content must stay at 0.30% or less. The withdrawal called for on 20 May 2026 targets CBD foods and supplements. The law of 24 February 2025 bans prefilled non-refillable devices and leaves bottles alone.
A well-purified CBD isolate contains no measurable THC. A full-spectrum extract or a poorly controlled liquid can contain some, and the law sets no minimum dose for drivers. Our guide to the saliva test explains this risk.
Some do and some do not. The label must say which, and a liquid with nicotine is also subject to the specific rules for nicotine-containing products.
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.