If you want to get into medicine, you are almost certainly going to need methods. It will greatly depend on where you would like to study at to the prerequisites and how much maths in the course.
Actually had a conversation about this with a friend studying at a science degree at Melbourne who is hoping to do Medicine. (Due to the Melbourne Model, you must first do a three-year general science degree and then postgraduate medicine.) He did methods and spesh and has still found the pace and content of the maths in his degree fairly difficult. To set yourself up well it would be advisable to do spesh, but it is not a prerequisite so it really depends on where you are studying. The prerequisites to get into an undergrad course at Melbourne vary slightly depending on which option you choose. There is a Bachelor of Science or a Bachelor of biomedicine but you can find more on
their website. This link may also be useful.
Monash's prerequisites are 30 in English or 35 in EAL and 30 in chemistry. They also recommend Year 12 biology, but have a bridging program if you haven't studied it. So if you wanted to study at Monash, you may be able to get away with just further.
Deakin has a postgrad medicine course (meaning you must have already done a University degree, similar to at Melbourne Uni). This means that there are not high school subject prerequisites but requirements about previous University marks ect.
There are also courses in other states which you may wish to look into, all having different requirements and different degrees of maths within them. Best of luck!
laura