depends on where you're from. i'm from jc and can only give jc perspective though!
pre-requisites for nus medicine will be H2 Chem and H2 bio or physics.
as for what's best,
H2 math is almost a must since without it you'll be ruling out a lot of 'back-up courses'.
as to whether to take H2 bio or physics, go for the one you'll more likely to appreciate and score better in since it's the final grade that matters.
however if you didn't take bio, when you enter the course you'll have to do some catching up with regards to biochemistry and some parts here and there while your peers who took biology are at ease. there are quite a number of people (maybe 20%) who didn't take bio. i would say take bio if you don't know whether to take bio or physics. but if you like physics a lot and can score then it's better to take phys.
in jc you can take h2 bio, chem, phys, math (ie. triple science + math) and for contrasting subject take H1 econs. that means you max-ed out your units and can't take H3 except for special cases.
there's also the portfolio, interview, essay tests for entering medicine.
Aiming for medicine course, which subjects to take?
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