Chemistry is vital for medicine, as is at least one other science.
Ideally, that would be bio, but physics is likely to be fine as well.
Just research each med school's entry requirements. Nobody here can explain every single medical school's policy on A level subjects.
As a side note, some medical schools just outright don't respect further maths while others will say that it can't be one of your 3 A2 subjects.
If I were you, I'd decide what I wanted to do as soon as possible. Med requires a good amount of WE/volunteering and ECs. If you want a strong med application, your best bet is to make an informed choice fairly early and completely commit to it.