While marijuana is generally prohibited in Islam due to its intoxicating effects and potential harm, its use for medical purposes may be permissible under strict conditions. These include necessity, medical certification of its benefits, and the absence of viable alternatives.

Conclusion: There is nothing wrong with you studying medicine and working as a doctor, whilst taking precautions to avoid matters concerning which there are shar‘i reservations. In fact, studying medicine is a beneficial field of knowledge, by means of which one may benefit and help people.