40 % CBD oil: what to know before buying one

The percentage shown on a CBD oil indicates the proportion of cannabidiol relative to the total volume of the bottle. At 40 %, roughly 4 ml out of 10 ml is made up of CBD and the other hemp compounds (minor cannabinoids, terpenes depending on the spectrum), the rest being the carrier oil, most often MCT, olive or hemp. This concentration remains well above the common ranges of 5 to 15 %, and even above the so-called "strong" formats of 20 to 30 %.

A 40 % oil makes it possible to reach a high dose with a reduced volume of liquid, which limits the pronounced taste and the number of drops required. It is aimed first and foremost at people already familiar with CBD, who have tried lower concentrations and are looking to reduce the volume administered for an equivalent or higher dose. It is not suited to first-time use: the gap between two drops becomes significant in mg, which complicates the fine adjustment sought during the initiation phase.

For a 40 % oil packaged in a 10 ml bottle with a standard dropper (around 200 drops per bottle), each drop delivers roughly 20 mg of CBD. A single drop therefore already represents ten times the provisionally safe daily dose published by the EFSA on 9 February 2026, set at 0.0275 mg/kg/day, or around 2 mg/day for a 70 kg adult. That gap illustrates why very concentrated formats demand particular caution and gradual adjustment, starting with a fraction of a drop, diluted if necessary.

A 40 % oil can be formulated as full spectrum, with traces of THC below the legal threshold of 0.30 % of the finished product, or as an isolate, with no detectable THC. Full spectrum keeps the minor cannabinoids and terpenes, at the cost of a more marked taste and a residual risk in saliva screening. The isolate offers a neutral profile, with no entourage effect claimed. Our article on full-spectrum CBD oil sets out this distinction in detail.

A 40 % CBD oil sold as an ingested food supplement falls under the Novel Food regime. Since 15 May 2026, the DGAL has been withdrawing ingested oils without European authorisation from the French market, whatever their concentration. Oils presented as cosmetics or for external use may still be sold, provided they carry no claim of ingestion or of therapeutic benefit.

CBD is not a medicine. A high concentration does not remove the need to start low and adjust gradually. If in doubt, consult a health professional.

Is a 40 % oil more effective than a 10 % oil?

Not in itself. What counts is the total quantity of CBD received in mg, not the percentage shown. The same dose can be obtained with several drops of a 10 % oil or a fraction of a drop of a 40 % oil.

Can a 40 % oil be diluted at home?

This is not recommended without the appropriate skills: mixing it with another oil alters the stability and traceability of the product. It is better to choose a concentration suited to your use from the outset.

Does a 40 % oil cost more than a 10 % oil?

The price per bottle is generally higher, but the cost per mg of CBD is often comparable, or even lower, thanks to economies of scale on concentrated formats.

Does an oil this concentrated need a specific certificate of analysis?

Yes, as does any CBD oil. The certificate of analysis (CoA) must confirm the real CBD concentration, the THC level below 0.30 % and the absence of contaminants, whatever the concentration shown.