What is the difference between prescribed and shop-bought CBD?
The bottle on a high-street shelf and the preparation dispensed by a pharmacy can both be called CBD, and they are not the same kind of thing at all. The difference is regulatory, and it has real consequences for what is in the bottle.
The short answer
- Shop-bought CBD is regulated as a food supplement, not as a medicine.
- Novel food authorisation covers safety, not effectiveness for any condition.
- No health claims may lawfully be made for a CBD food supplement.
- Independent testing has repeatedly found content differing from the label.
- Prescribed preparations are pharmaceutical, with specified and tested content.
Two different regulatory worlds
A product's category determines what standards it must meet, what testing is required, and what may be said about it. CBD sits in two categories at once depending on how it is sold, which is the root of most of the confusion around it.
The same molecule can be a food supplement in one context and a component of a medicine in another. What changes is not the chemistry but the framework around it: who checks it, to what standard, and what the seller is allowed to tell you. Keeping that in mind makes the rest of the comparison much clearer.
| Shop-bought CBD | Prescribed preparations | |
|---|---|---|
| Legal category | Food supplement (novel food) | Medicine — licensed or unlicensed |
| Regulator | Food Standards Agency | MHRA |
| What approval covers | Safety for consumption | Quality, and for licensed products, efficacy |
| Content verified batch to batch | Not required in the same way | Yes, to pharmaceutical standards |
| Health claims permitted | No | Only within the terms of a licence |
| Clinical oversight | None | Specialist prescriber and pharmacist |
The novel food route matters here. Authorisation under it is an assessment of whether a product is safe to eat. It is not a finding that the product works for anything, and it does not permit the seller to say that it does. This is an easy distinction to miss, because the word "authorised" sounds like an endorsement. It is closer to the clearance any new food ingredient must obtain before it can be sold, and it says nothing at all about treating a condition.
What is actually in the bottle
Independent analyses of consumer CBD products in the UK and elsewhere have repeatedly found actual content differing from the label — sometimes substantially less than stated, occasionally more, and in some cases detectable THC in products sold as THC-free. The finding is consistent enough across studies that it should be treated as a feature of the market rather than the occasional bad batch.
That last point has practical consequences beyond value for money. A product containing more THC than its label suggests can create difficulties with workplace testing and, in principle, with driving. Someone buying a supplement marketed as THC-free would have no reason to expect either problem, which is precisely what makes an inaccurate label more than a consumer-rights issue. The related questions of driving and workplace testing are covered in Driving with a medical cannabis prescription and Medical cannabis, drug testing and work.
It is also worth knowing that the amounts of CBD in typical consumer products are far below those used in the trials that established the licensed medicinal use of purified cannabidiol. Comparing the two as though they were the same intervention is not reasonable. Someone taking a low-strength supplement and someone taking a licensed medicine at a trial-level dose are, in effect, doing two quite different things, even though both bottles say CBD. This is one of the most common misunderstandings people bring to a consultation, and it is worth clearing up early.
If you are already taking shop-bought CBD
Tell your prescriber and your GP. It is a substance with real pharmacological activity and real interactions, and it belongs on your medicines list alongside anything else you take, including supplements and over-the-counter products.
CBD affects the enzymes that metabolise a number of other drugs, which means it can change the levels of medicines you are taking for something else. That is true regardless of where it came from. The effect does not depend on the product being a medicine or a supplement; it depends on the CBD itself. This is why "it's only a supplement" is not a reason to leave it off your records — from a pharmacological point of view, your body does not distinguish between a prescribed source and a high-street one.
None of this is an argument that shop-bought CBD is dangerous or that people should not use it. It is an argument for being clear about what it is: a supplement with variable content, no permitted health claims, and no clinical oversight — which is a different proposition from a prescribed medicine.
How prescribed cannabis-based medicines differ in practice
Where CBD is prescribed, it is part of a medicine chosen and supervised by a specialist, not a product picked off a shelf. That oversight is the substance of the difference, not a formality — it is what turns a substance into a treatment plan tailored to one person.
A prescribed cannabis-based product is considered only after a specialist has reviewed your diagnosis, the treatments you have already tried and your wider medical history. Where one is judged appropriate, it is typically started at a low dose and adjusted gradually, with follow-up reviews to check whether it is helping and whether side effects are tolerable, and it may be changed or stopped if it is not. How that is done is set out in How is a dose decided and adjusted? Whether it is appropriate at all is an individual decision, and some people are advised that treatment is not suitable for them.
It is also worth knowing that CBD is only one part of the picture. The other main compound, THC, carries most of the significant risks in this field, and the balance between the two is one of the things a specialist manages. The difference between them is explained in What is the difference between THC and CBD?
Reading a shop-bought CBD label
If you do buy CBD as a supplement, a few habits reduce the chance of being misled and keep you and your clinicians safe.
- Treat health claims as a warning sign. A CBD supplement may not lawfully claim to treat or prevent any condition; a product that does is breaking the rules, which says something about the seller.
- Assume the stated amount is approximate. Independent testing has repeatedly found content differing from the label, so the figure on the bottle is not a guarantee.
- Remember "THC-free" is not always accurate. Detectable THC has been found in products sold as free of it, which can matter for driving and for workplace testing.
- Put it on your medicines list. Tell your GP, pharmacist and any prescriber, because of its interactions with other drugs.
These are practical points rather than reasons for alarm. The aim is simply to treat a supplement as what it is, and a medicine as what it is, without confusing the two — a distinction that becomes especially important if you go on to be assessed for a prescribed cannabis-based medicine.
Frequently asked questions
Is shop-bought CBD the same as prescribed CBD?
No. Shop-bought CBD is regulated as a food supplement by the Food Standards Agency, which assesses safety for consumption rather than effectiveness. Prescribed preparations are medicines regulated by the MHRA with specified, tested content.
Can CBD products make health claims?
No. A CBD food supplement may not lawfully be advertised as treating or preventing any condition. Where you see such claims, they are being made in breach of the rules.
Does shop-bought CBD contain what it says?
Not always. Independent analyses have repeatedly found content differing from the label, including detectable THC in products sold as THC-free — which can matter for workplace drug testing.
Should I tell my doctor I take CBD?
Yes. CBD affects the enzymes that metabolise several other medicines and can change their levels in your body. It belongs on your medicines list wherever you bought it.
Is prescribed CBD stronger than shop-bought CBD?
The two are not directly comparable. Prescribed preparations have specified, tested content and are used under clinical supervision, while consumer products vary and typically contain far less CBD than the amounts studied in the trials behind licensed medicinal use. Strength is only one difference; regulation and oversight are the larger ones.
Why is shop-bought CBD so much weaker than the amounts used in trials?
Consumer products generally contain far lower amounts of CBD than the doses used in the trials that established the licensed medicinal use of purified cannabidiol. Comparing the two as though they were the same intervention is not reasonable.
Is shop-bought CBD legal in the UK?
CBD food supplements are sold lawfully under food regulation, but they may not make health claims and must meet the rules on controlled substances such as THC. Where a product makes health claims, those claims are being made in breach of the rules.
If I start a prescribed medicine, should I keep taking shop-bought CBD?
That is a question for your prescriber, who needs to know about everything you are taking. Combining products without telling anyone risks unexpected interactions and makes it harder to tell what is actually helping.
Sources and further reading
Every factual statement on this page is drawn from the following public sources. Links open in a new tab and are not affiliated with Flora House.