For medical schools that just look at minimum GCSE grades (e.g. UCL, Imperial) then yes, it's fine, as they will just tick you meet that requirement and then move on.
For medical schools that formally score GCSEs (e.g. Oxford, Cardiff), then it may mean you won't be able to get maximum points in that part of the application which may be the difference between getting an interview or not. For some though the methodology they use to score them may mean you can still achieve the maximum in that part of the shortlisting process.
In either event you should carefully review the shortlisting methodology of the medical schools and work out which ones you will score the maximum points in shortlisting to maximise your chances of getting an interview (and hence, a chance at an offer).