There is no government medical cannabis card. You must first see a specialist...

https://oscar-wiki.win/index.php/What_is_the_Difference_Between_a_Cannabis_Prescription_and_a_Cannabis_Card_in_the_UK%3F

There is no government medical cannabis card. You must first see a specialist who reviews your medical records for a prescription. Once prescribed, an optional card serves as proof of lawful use for the police or public