I retook 6 classes total, most resulted from not taking my education seriously during my freshmen year. Bio I and II (got C's in both first round), Physics I, Genetics (C-), Orgo I (D), and Microbiology (C). Yes. I retook classes I got C's in. A lot of people don't recommend doing so and that you should just take upper science classes instead. Well, I was a science major so I took pretty much all the science classes my school (private) had to offer. Since my GPA wasn't where I wanted it to be I decided to retake those classes I got C's in the first time but know for sure I could get at least a B or an A in the second time around. I replaced all those with A's.
Out of the four interviews I went on no one ever question the number of classes I retook.