I suppose we will all give slightly different answers to this as we will have all done slightly different A Levels! I studied Maths, Biology, Chemistry and Spanish at A Level, and the biology especially came in useful for the first two years of medical school as this was predominantly spent learning about the human body and how it works. The chemistry was also helpful but less so.
In my day to day work now however I don’t use these very often – they tend to be more useful if I go to a pub quiz or something like that! On the other hand I do use my Spanish sometimes – for example a couple of months ago when I was working in A and E I had a patient who had broken her arm on holiday in Spain and I was able to read the letter she had got from the hospital in Spain which helped me to know what treatment she had received and what we needed to do to help her then!
A levels serve two purposes: to get you into whatever career you want, but also to teach you about stuff you find really interesting. So I did some highers (I was in Scotland!) which helped me to do medicine (biology, physics, chemistry) but some because I liked them and was interested in them (german) and some because I was forced to! (english, maths).
In the first week of university they pretty much went through a whole A level in a single lecture, which slightly terrified me, but the teaching was really good so I did manage to keep up. It was a bit of a shock to the system to go from top of the class to “distinctly average” but I did adjust quickly.
Biology was probably the most useful subject & chemistry. Didn’t really use physics.
The first few years of medical courses build on biology and chemistry from A level and although you obviously learn more it helps make understanding new things and explaining them to patients much easier.
I did history too which was useful for developing skills around writing, research and analysing evidence, which is very important in keeping up to date with medical studies and new practices. So if you enjoy music, English, drama, languages etc then don’t stop just because they’re not sciencey – medicine uses lots of different skills!