I think when it comes to medicine (premed, med school, and beyond), hard work and persistence is key. Without it, I don't think anybody even with a super IQ will succeed. Most people with high IQ like to get quick results without lots of effort, obviously because they don't have to. To be in medicine is a bit counter intuitive for them.
I must say that my IQ is above average (140) and I do prefer doing math (I'm a Math major) than memorizing intro biology because I don't have to study (or very little) for math. In fact, in some of my math courses, I never attended the lecture, only came for the exams, and still got solid As. But for orgo, bio, etc., I had to come to the lecture (dammit).. I disliked the learning process because I had to memorize a lot (more memorization than comprehension, unfortunately). I did, however, only had to read once or most, twice, for courses like psych or history just to pull an A. (I'm lazy in a way). I managed to pull all As in my science courses (other than math) because I actually studied and read the books (shocker!). It has been a humbling experience, I must say. Maybe those with IQ 160 and above would not need to study, but in general, without hard work, I probably would have flunked.