back on topic,
OP for medicine in the US you will need to complete an undergraduate degree first with a GPA of usually 3.4 or above, of which places will be very competitive for (you'll want to get some extra-curricular's as well because they love those) combined with the requirement of doing SAT's which cost a bucket load and the cost of tuition and room and board if you don't get into a top uni which gives out full scholarships like they're cup cakes. Then you really need to acquire citizenship otherwise the med schools won't be as eager to admit you due to the financial side of things, also because if you don't get a scholarship it spreads out the cost as some med schools ask for a lump sum at the beginning of around $200,000 from internationals whereas you can get a student loan from FAFSA if you're a citizen.
for the UK you'll want to get high marks (usually 80%+) and study up on your English, you'll also need some work experience as well to show that you know what doctor's do exactly.