From all the applicants for medicine, how many would you assume do maths? Not doing it makes you stand out. Most institutions teach maths, therefore an applicant wanting to do medicine needs a good reason not to. Not to mention from all my friends that are applying to medicine, they all do maths (9 people).
Furthermore, a study I read recently says that a good 50+% (I forget precise numbers) of Oxbridge's humanities students take maths. So with that reasoning, not taking maths in a 'science-y' course could be a let down.
Additionally, as a student myself taking Maths, Biology, Chemistry and Physics, I can honestly say, looking at myself and my classes, maths is a significant boost to my studies, not to mention understanding topics when reading around my subjects.
Nevertheless, I hope the OP does what's best for them, and I wish them every success in the future.
Thanks.
P.S.
www.examsolutions.net is a great resource for maths, from a-levels to GCSE. Includes all boards and past paper solutions.