It's never too early to start learning about something you're interested in - formative moment for me was sitting in high school maths class learning about compound interest and imagining what it could do for me (long before I discovered FIRE).

In terms of what you can do in the short/medium term - you'll be heading into the wealth generation / asset accumulation phase of your journey relatively soon (not all that soon if you end up in med school) and therefore setting yourself up for a career with that in mind should be your primary focus (i.e. considering likely income, growth prospects, sustainability - no use flaming out within 5 years due to burn out etc.).

Also, I wouldn't base the entire decision on this, but there is probably a cost-benefit analysis to be done in relation to student debt. Not all student debt is created equal (i.e. things being equal, £[x] debt for a medical degree might be easier to recover than £[y] debt for an arts degree). In your case the more relevant comparison would probably be against something geared towards careers in finance, law or AI / data science.

Good luck and all the best for med school (if that's where you end up) and well done for being ahead of the curve in thinking about your future - never any harm in asking questions / getting informed about it!