I'm sorry but i don't agree. Yes your supposed to get good grades, meaning A- to A's but at the same time, ive been told by multiple faculty members at the medical school i'm interested in (top 30 school) that they really prefer students who challenged themselves in undergrad. Additionally, i've ASKED the question about taking 12 credits per semester or in other words less than the usual 15-16 and i got the same answer from all of them. You really should only take at most 1 semester of 12-13 credits in your undergraduate education. Just find some stupid filler class and get it to 16 to cover your bases. If taking 16 credits really means that you can't achieve A's then you you really should re-evaluate your priorities