Video report by ITV News Consumers Editor Chris Choi
There are new concerns about a popular food supplement derived from cannabis known as CBD.
Cannabidiol, or CBD for short, is the non-intoxicating component in marijuana, which means it can't get you high.
It's used in a huge range of products, but pharmacists say not enough is known about it and want tighter regulations.
ITV News has also uncovered evidence that some customers are not getting what they paid for.
Around three million people in the UK have tried CBD, which claims to treat conditions such as chronic pain, PTSD and epilepsy.
Recent studies of medical marijuana suggest CBD can have a positive impact on patients with epilepsy.
Sold in everything from drinks and chocolate, to oils and lotions, CBD sales are booming - but regulations are struggling to keep up.
When the Cannabis Trades Association tested 2,000 online products, about 1,000 contained no CBD or less than stated, ITV News has learnt.
Jas Nottay, of the association said: “A lot of consumers will be quite angry, I would imagine, they’re spending pretty good money on these products and to hear that it’s not what they’re buying I imagine is not going to be a good feeling at all.”
The trade is now working on a quality mark for products that pass independent tests.
But pharmacists are calling for officials to step in.
Jasmine Shah, National Pharmacy Association, said: “We would welcome some clear, authoritative guidance so that health care practitioners, consumers, manufacturers can all make informed choices.”
Some customers say it helps with stress, but as officials try to catch up with a rapidly growing market, CBD could well cause them growing anxiety.