Cannabinoid reference entry
THC
THC is the name that carries the most practical risk questions
THC usually means delta-9-tetrahydrocannabinol. The NHS distinguishes it from CBD and describes THC as the compound associated with the high from cannabis. A percentage on a label is still only a concentration measurement. It is not a measure of benefit, suitability or a person’s actual impairment.
A controlled human experiment shows why context matters
In a double-blind laboratory challenge, healthy participants received intravenous delta-9-THC. The study recorded temporary psychosis-like symptoms, altered perception, anxiety, euphoria and impairment on several cognitive tasks. This was experimental exposure in healthy people, not a trial of a prescribed UK cannabis product and not a prediction of every patient’s response.
Another randomised human study examined oral THC with different CBD coadministration conditions. The exposure and subjective effects changed with the formulation and co-administered cannabinoid. That finding does not produce a universal THC:CBD ratio rule. The CBD reference explains the separate evidence base for that compound.
THC numbers need legal and clinical context
The NHS describes risks associated with THC-containing products. The Home Office sets out the controlled-drug framework for THC and cannabinol derivatives, including cannabis-based products for medicinal use. UK driving law also distinguishes impairment from the prescribed-medicine circumstances in its guidance. A label cannot provide driving clearance, and the number cannot replace the prescribed instructions or a clinician’s assessment.
THC findings vary with route, formulation, setting, previous exposure and the people taking part. That is why a THC figure should remain a composition detail rather than a dosing or product-selection rule.
Related conditions
Sources
- The psychotomimetic effects of intravenous delta-9-tetrahydrocannabinol in healthy individuals (human controlled laboratory study, 2004).
- Assessment of orally administered delta-9-THC when coadministered with CBD (human randomised pharmacokinetic study, 2023).
- Medical cannabis (NHS, accessed 2026).
- Drug licensing factsheet: cannabis, CBD and other cannabinoids (Home Office, 2024).
- Drugs and driving: the law (GOV.UK, accessed 2026).
For a plain-English glossary explanation, read THC.