In the UK, THC is a controlled substance under the Misuse of Drugs Act 1971. Products that contain THC are only legal if they meet strict exemptions. The key rule is that consumer products must contain less than 1 mg of THC per container, regardless of concentration. Anything above this is classed as an illegal controlled drug unless prescribed.
THC as a controlled substance
THC, or tetrahydrocannabinol, is listed as a Schedule 2 controlled drug. This means possession, sale, or supply is generally prohibited without a prescription. Unlike cannabidiol (CBD), which is not a controlled substance, THC is regulated because of its psychoactive potential.
The law does not refer to a percentage limit like 0.2%. That figure applies to hemp cultivation rules in Europe. UK law is based on total content: a container cannot exceed 1 mg of THC to qualify as exempt.
Medical cannabis exemptions
Since 2018, specialist doctors in the UK have been allowed to prescribe cannabis-based products for medical use in humans (CBPMs). These may contain THC, but prescriptions are only given under strict conditions, usually for severe conditions such as epilepsy, multiple sclerosis, or chronic pain. Outside of a prescription, the threshold of less than 1 mg per container applies.
What this means for vapes and other consumer products
For vapes, oils, or edibles to be legally sold without a prescription, they must be manufactured so that the entire cartridge, bottle, or package contains less than 1 mg of THC. If the same product were to exceed that limit, it would fall under the controlled drug law.
This rule explains why legal low-THC vapes in the UK do not cause intoxication. They contain trace levels of THC, often paired with CBD or other cannabinoids, but always kept under the 1 mg threshold. Consumers may notice mild relaxation or flavour effects, but never the strong “high” linked with higher-THC cannabis.
Practical examples
- A vape cartridge containing 0.8 mg of THC in total is legal to sell.
- A bottle of oil with 1.2 mg THC, even if diluted in 30 ml, would be illegal without prescription.
- A CBD edible must ensure its total THC content remains below the 1 mg limit to be legally sold.
For context on how THC works in the body, see: What is THC?
To understand how long THC can remain detectable, see: How long does THC stay in your body?
Consumer choices
For everyday consumers, the key point is simple: only low-THC products with less than 1 mg per container can be bought legally without a prescription. This ensures safe, compliant use without risk of prosecution.
