The numbers do not add up
There is a fundamental disconnect at the heart of the UK CBD market, and most brands would rather you did not notice it.
Clinical studies investigating CBD for conditions like anxiety, sleep disorders, and chronic pain typically use doses between 150mg and 600mg per day. Some epilepsy studies use doses as high as 20mg per kilogram of body weight per day.
In October 2023, the Food Standards Agency reduced its recommended maximum daily intake for over-the-counter CBD to 10mg per day for healthy adults.
Most CBD products on the UK market suggest daily doses somewhere between 20mg and 70mg — higher than the FSA recommends, but far lower than the clinical research uses.
This is not a minor discrepancy. It is a chasm. And understanding why it exists is essential for anyone spending money on CBD products.
Why the FSA set the limit at 10mg
The FSA's 10mg recommendation is based on a safety assessment, not a therapeutic assessment. The distinction is critical.
The Committee on Toxicity (COT) examined the available evidence and established a provisional acceptable daily intake (ADI) based on what they could confidently say was safe for the general adult population with long-term daily consumption. The ADI is calculated as 0.15mg per kilogram of body weight per day, which for a 70kg adult works out at approximately 10mg.
This figure is conservative by design. Food safety regulators apply uncertainty factors — essentially safety margins — to account for individual variation, gaps in the data, and the difference between controlled study conditions and real-world consumption. The 10mg figure is not the point at which CBD becomes dangerous. It is the point below which the FSA is confident it is safe for virtually everyone.
It is also worth noting that the 10mg ADI was a significant reduction from the previous guidance of 70mg per day. The FSA revised it downward after new toxicological data became available, which underlines that our understanding of CBD's safety profile is still evolving.
Why clinical studies use much higher doses
Researchers studying CBD for specific therapeutic applications are asking a different question from the FSA. They are not asking "what is safe for everyone as a daily food supplement?" They are asking "what dose produces a measurable therapeutic effect for this specific condition?"
For anxiety, the answer appears to be somewhere around 300mg for an acute dose, based on the inverted U-shaped dose-response curve identified by Linares and colleagues in 2019. For chronic pain, doses in the studies typically range from 150mg to 600mg daily. For epilepsy, the approved pharmaceutical Epidyolex uses doses of 5-20mg per kilogram of body weight — which for a 70kg adult could mean 350mg to 1,400mg per day.
These are pharmaceutical-grade doses administered under medical supervision, with standardised products of known purity and concentration. They are not directly comparable to taking drops of an over-the-counter oil from a health food shop.
The bioavailability factor
The dosage picture is further complicated by bioavailability — the proportion of CBD that actually reaches your bloodstream and produces an effect.
When you swallow CBD oil, it passes through your digestive system and liver before entering your bloodstream. This first-pass metabolism significantly reduces the amount of active CBD that reaches systemic circulation. Oral bioavailability of CBD is estimated at somewhere between 6% and 19%, depending on the study and the formulation.
Sublingual administration (holding oil under the tongue) bypasses some of this first-pass metabolism, potentially improving bioavailability. This is why most CBD oils recommend sublingual use rather than simply swallowing the oil.
What this means in practical terms: if you consume 10mg of CBD orally, somewhere between 0.6mg and 1.9mg may actually reach your bloodstream. If the clinical studies showing anxiety reduction used 300mg, the amount reaching the bloodstream in those studies was approximately 18-57mg — still dramatically more than what a 10mg consumer dose would deliver.
Some brands are now using nanoemulsion technology or lipid-based delivery systems that claim to improve bioavailability. These claims have some scientific basis — encapsulating CBD in nano-sized lipid particles can increase absorption — but the specific improvement varies by formulation and independent verification of these claims is often lacking.
So what dose should you actually take?
This is the question everyone asks, and the honest answer is that we cannot give you a definitive number.
What we can tell you is this.
The FSA recommends no more than 10mg per day for healthy adults using over-the-counter products. This is the official safety guidance and it would be irresponsible for us to recommend exceeding it.
The clinical evidence for therapeutic effects comes from doses far exceeding 10mg. If you are seeking specific therapeutic benefits, the over-the-counter route may not be sufficient, and a conversation with your GP about prescribed cannabis-based medicines may be more appropriate.
Individual responses vary significantly due to differences in endocannabinoid tone, body composition, metabolism, and the specific condition being addressed. What works for one person may not work for another at the same dose.
If you do use CBD, starting at a low dose and observing your response before adjusting is the most commonly recommended approach. Keeping a simple daily log of dose, timing, and any perceived effects can help you identify whether CBD is doing anything meaningful for you personally.
The honest summary
The gap between clinical research doses and the FSA's recommended daily limit is real, significant, and not adequately addressed by most CBD brands. The FSA's limit is based on safety, not efficacy. The clinical doses are based on efficacy, under medical supervision.
This does not mean that over-the-counter CBD at lower doses is worthless. Individual responses vary, and some people report benefits at doses well below those used in clinical research. But it does mean you should have realistic expectations, be sceptical of brands promising clinical-grade results from food-supplement-grade doses, and consider whether a conversation with a medical professional might be more appropriate for your specific needs.