Apparently double edge blades are not considered "safety razors" under the permitted rules of what's allowed in a carry-on bag.
Without going into detail about my experience (which may vary from yours because I carry a badge), suffiice it to say that you should not attempt to bring a loaded double edge razor on-board with you. Do some research before travelling to find out where you can get your blade of choice at your destination.
This should remove any doubt! (Previously I was of the opinion, because of discussions with a TSA supervisor, that one single DE blade loaded INTO a razor would be allowed because it's a 'safety razor' and 'disposable' under the guildelines of what's permitted under TSA rules... I was wrong!)