I'm applying for Medicine this year with my final results. I started IB with HL Bio, Chem, English and Maths, and dropped Maths to SL after a year because I was struggling to get 4's at HL (and I got an A* in IGCSE Maths, A in Add Maths). It was really, really hard for me, and dropping to SL afterwards was sort of like sitting the IGCSE exam for the second time with a few extra topics.
Having said that, though, exam results (and sometimes even your teachers' recommendations) really aren't everything. If you don't think your IGCSE Maths grades reflect your expectations/potential, you're very good at Maths, and you really enjoy it, I'd try out Maths as a fourth HL along with Bio, Chem and English/History, and see how you cope. All but one person in my HL Maths class did that, and three of us dropped to SL at the end of the year with three other HLs to fall back on. The others dropped one of their other HLs instead because they could cope with the workload.
As to whether you need it, though, I don't think I've ever seen HL Maths specified for Medicine (I can't speak for the other two courses, but I imagine it would be the same). If they don't mention that they'd prefer HL Maths in the prospectus/website, you could probably assume that your third HL won't matter.
If you're applying to Oxbridge, though, some colleges do prefer three science/maths A-levels, which could equate to three science/maths HLs. Email and ask them to be sure. The other colleges should be fine though - I recently emailed the admissions office at Sidney Sussex in Cambridge to ask the same question and got this reply:
"The Pre Clinical Medical Requirements state that you need to have done three out of the three sciences + maths, but not all need to be to A-level (or Higher Level, although I know these are not synonymous). On the whole, most applicants would offer a third science/maths at Higher, but as it is not compulsory, we cannot disadvantage anyone for not having it!"
So basically, Bio and Chem HL are fine, but take Maths HL if you really like it and feel you can cope.
I didn't take (and didn't like) History so I can't really answer your question fairly, but I can tell you that English HL is brilliant
if you love English Lit. It's much less straightforward than IGCSE because you do about 16 works, you write your own coursework questions, and the exam questions are bizarre but pretty fun to try to make sense of, so it's very self-directed. But I'm totally biased
And woooww that was a long post.