Having finished the 9th season, I know my review may seem hypocritical, as I am only 11. I believe that age doesn't matter really, when it comes to Grey's Anatomy, as long as your child is mature. Yes, it includes gore and blood, in surgeries, and that may scare some. However, this addictive series is most definitely a must-see.
There are sexual scenes where people are in bed together, although no nudity or anything too severe. I would recommend this to anyone mature enough to watch it. Honestly, in this new generation, the internet is full of dodgy things; things your child is almost certain to encounter. If they know about this sort of stuff, limiting them has no purpose. If they know about sex, this show is harmless.
As far as language goes, if your kid has not started swearing by the age of 12. I'm sure mild language in a TV Show will influence them to do so.
Deaths of some characters can be heart-breaking, however, heart-break is not rare in life. In some perspectives, it prepares them, which is actually quite beneficial.
Characters are really ambitious to become a great surgeon, which I believe is very positive. Also, as doctors, they save lives every day. Therefore, they could be considered as role-models.
In conclusion, I recommend that you do more research about this show, and really consider on how it would actually affect your child. As I currently believe it's not dangerous for your child in anyway.