The United Kingdom legalized medical cannabis in 2018, yet little is known about people using cannabis medically with and without a prescription. This study aimed to estimate: 1) the percentage of people reporting using cannabis medically with and without a prescription; 2) the sources; 3) products used; and 4) associations between frequent product use and medical cannabis status.

Data were from national repeat cross-sectional surveys conducted in 2023 and 2024. UK participants were aged 16–65 who used cannabis in the past 12 months (n = 4,414). Multivariable regression analyses estimated associations between outcomes and medical cannabis status.

Overall, 12.9% of respondents reported receiving a medical cannabis prescription, 35.9% reported medical use without a prescription, and 51.2% reported no medical use. Cannabis was sourced through diverse routes; only 10.9% of people with prescriptions obtained all their cannabis from a prescription. Respondents with a prescription had a higher probability of reporting frequent use of drops, capsules, vape oils, edibles, drinks, solid concentrates, hash/kief, and topicals (aRRs = range between 1.82 and 3.51)) and a higher probability of screening positive for high-risk use (aRR = 3.09; 2.51–3.79) than respondents who did not use medically.

People with medical cannabis prescriptions show a higher probability of frequent use of processed products and of meeting a threshold for high-risk use. Healthcare encounters during medical cannabis prescribing should discuss risks related to products, potency, and adverse effects such as cannabis use disorder.