Buying It Safely
A sensible dose, who should avoid it entirely, and how to buy something that's actually what the label says, in a market where often it isn't.
How much, and who should avoid it
Even though it won't get you high, CBD isn't a "more is automatically fine" substance. Based on evidence about possible effects on the liver and thyroid and interactions with medicines, the FSA advises that healthy adults have no more than 10mg of CBD a day from food unless a doctor says otherwise. That's a small amount, and many products deliver more than that in a single recommended serving (FSA, 2023).
The FSA is also clear that some people should avoid CBD altogether: anyone who is pregnant, breastfeeding or trying to conceive, and anyone taking medication, unless a doctor has said it's fine, because CBD can interact with other drugs. If you're on any prescribed medicine, check with a pharmacist or GP before adding CBD, rather than assuming "natural" means "no interactions."
The quality problem
Here's the part the industry is quietest about. With a loosely-regulated market, what's on the label frequently isn't what's in the bottle. STRONGEvidence strength Independent testing repeatedly finds CBD products mislabelled, containing substantially more or less CBD than claimed, and sometimes containing THC that shouldn't be there at all. Key study: Bonn-Miller et al. (2017), JAMA tested CBD extracts sold online and found only around a quarter were accurately labelled. Most contained more or less CBD than stated, and about one in five contained detectable THC. What it means for you: a CBD dose you can't trust is a dose you can't judge, and an unexpected trace of THC matters if you're ever drug-tested.
The practical defence is boring but effective: buy from established brands that publish a recent, independent lab report (a "certificate of analysis" / COA) for the exact product and batch, prefer products on the FSA's public list, and be sceptical of anything sold mainly on bold health promises or a suspiciously low price.