Generally it's going to be as many A* grades as you can achieve and with the subjects that you didn't get an A* in, they should be filled with As but the occasional 1B will not have an impact. Its fair to say that most people who want to apply for medicine, will want to have a choice of a wide range of universities so they tend to MAX out all the requirements for medicine, this includes getting 7-10 A*s... But of course some people wouldn't quite reach that number but as long as you solidly pass the GCSE requirements, you can get into medicine, it just means your choice of university will be decreased - and i don't see this as a huge problem because if you haven't noticed already there is no non-russel group university that offers medicine, so as someone said earlier, there is no such thing as a 'top medical school'. In other words, if you do not care which university you end up going to as long as you get into medicine, passing the GCSE entry requirements 'comfortably' should leave you in a good starting position.