Hi,
A lot of universities consider your best 9 GCSEs - of me and my friends who have applied to medicine this year and got offers, for most people, most of those 9 have been A*s with a few As. Different unis will place different emphasis on your GCSE grades - some look at them perhaps as close as/more closely than AS levels (eg Queen's Belfast) whilst others are more concerned with things like AS grades, personal statement, community service, etc. If you're applying this year then start researching now what university looks for people with your strengths - medicine is more competitive than ever now and I know plenty of exceptionally intelligent people (8A* and above) who did not get offers simply because they didn't play to their own strengths when making choices.
David