The microsecond you become a dog owner, you suddenly lose all tolerance for seeing dogs injured or killed in entertainment. This is absolutely ridiculous, mind you, but if you own a dog, it’s going to happen. So, it’s with great relief that I report to you that Dogmeat is immortal in Fallout 4.
This is actually straight from Bethesda itself:
So, don’t worry. No matter how terrible a shot you are, no matter what you run into in Boston, your friend Dogmeat won’t die. That doesn’t mean he can’t be injured, and I suspect we’ll see a whole bunch of videos delivering swift and painful vengeance on any foe who targets Dogmeat, but at least you won’t have to bury your dog amidst the ruins of civilization.