It depends on which university you attend. Check out the following link for how GPA conversions are done for Ontario medical school applicants:

http://www.ouac.on.ca/omsas/pdf/c_omsas_b.pdf

I don't quite understand what you mean by high school level.

I had a 3.98 GPA after two years, and for sure it wasn't easy to keep that GPA up – I also think I got pretty lucky in some courses, where I marginally aced.

Like anything, getting good grades is a combination of how difficult the courses are (for you personally), how much effort you're willing to put into it, the type of preparation you do, and luck.

was it very hard to keep that high GPA?

Eden: These things are always super competitive. Besides obvious things like GPA and MCAT scores, it's hard to know what admissions committees are looking for a lot of the time. Plus, there is quite a bit of variance involved – who readers your application, how they're feeling, etc.

I've heard of students who got an interview one year, sent a self-proclaimed improved application the following year, and did not get an interview from the very same school. And then there are students with the exact opposite experience.

The good thing about medical school admissions is that you can apply every year… much better than some things where you only have one shot.