I think if you can get your doctor to write a letter detailing that you NEED this card, then it helps a lot.
My GP wrote a brilliant letter, stating that he thought I would stop my meds and various other things if I didn't get help, as the medical bills were so high I simply couldnt afford to keep it up.
Since I have a long term illness, I got my card back for three years, and without my doctors help, I dont think it would have happened.