If you're working at 7/8 A*s you're doing great! The med schools that heavily weight on GCSEs tend to have a scoring system; for example, Nottingham look at (at least when I was applying) your top 8 GCSEs and for each A*, you'd get a certain number of points, for each A you'd get the points for the A*-1 and so on Even if the D was in your top 8, you wouldn't get points taken away from your score (no negative marking woo)
I know people at med school with a lot less than 7/8A*s so you I don't think it'll affect you much at all!
That's encouraging! Thanks for the reply! Btw how did your application go?