Third alevel subject for medicine

Taking A Level Art is fine. The only uni that prefers a 3rd STEM subject is Cambridge, the rest won't mind.

I want to do medicine so I will be taking bio and chem but im also passionate about art alongside stem so I wanted to do alevel art and I talked to my career advisor about this and he said for medicine I must take either maths or another science as this is what unis prefer. But I've seen a lot of different opinions on this so do unis prefer any specific alevel subjects?

Many medical schools require your third subject to be in a science or maths subject, so it's important to look at university websites to see what subject requirements they ask from you. In addition, even if universities aren't particularly bothered about your third subject, having your third subject in maths or another science will prove especially useful in transferable skills, and may potentially make your application stand out more, so it's important you do your research. However, you can always make up for making other parts of your application stand out, e.g. UCAT, interview, personal statement, work experience, etc. Hope this helps! Also, you may want to consider doing four A-Levels (I do biology, chemistry, maths, and further maths, and am also looking at medicine).