What he may not know is that if the metformin does not work because he is eating to many carbs the doctor will have no alternative but to put him on other medications that by law he will have to declare to dvlc and his vehicle insurance. Then he will have to test before every single journey and if his blood sugar is not within range he will not be allowed behind the wheel until it is. this will cause a lot of difficulty I imagine. Then there is retinopathy, although this can usually be alleviated with lazer surgery certain lazer surgeries lead to permanent loss of your driving license due to being left with tunnel vision. food for thought, pun intended.
Wow I didn't realise this. Thank you, I'll mention this to him and see if that helps to motivate himself.