Cannabis prescribing was legalised in the UK in 2018 but remains otherwise criminalised. There are approximately 45000 legal patients who are reliant on private clinics, given that fewer than 5 people have been able to obtain a National Health Service (NHS) prescription. It is estimated that a further 1.8 million people each day take cannabis for medical reasons without a prescription. This paper presents emerging findings from a qualitative study of the experiences of people who self-medicate with cannabis, operating outside the legal prescribing framework by obtaining cannabis on the illicit market or growing their own. Firstly, we introduce the UK policy context in which people who need cannabis medicine face barriers to legal prescriptions, including financial constraints and stigma. Secondly, we draw on in-depth interviews (n = 26) to explore the experiences of people accessing medical cannabis from illicit sources. We consider their reasons for accessing cannabis without a prescription and the risks they are potentially exposed to, including criminalisation. Finally, we reflect on some of the implications of the UK’s drug policy for people who need cannabis medicine.