Can I use Mass Effect 3 DLC while offline?

I haven't verified the work around, but I can confirm that on a PC with origin, if you have any kind of DLC linked to your account you must be connected to the internet long enough to load your save. If you are disconnected at any time prior to that you will not be able to load your save or do anything really except start a new game.

Short answer: No offline play with DLC.

It seems like it does authenticate every time, and if you're not able to authenticate, you won't be able to load that DLC on a subsequent run. It seems like it might even lock you out of a save created with DLC if you're unable to authenticate said DLC, but I'm looking for official confirmation of this.

One poster on the Bioware forums posted this workaround, although it requires that you have internet access at least enough to authenticate for a little while:

1. Start Origin.
2. From Origin, Start Mass Effect 3.
3. Wait for all of your DLCs to authenticate then load a save game. If you are in Normandy Shuttle Bay area, check if your CE items and Preorder bonus are there, if they are then Save game and exit to Main Menu then close.
4. Just close Origin, remember just close and not Log Out or Play Offline.
5. Disconnect from the internet.
6. Use the desktop shortcut of Mass Effect 3 to start game, NOT ORIGIN.

I launched Mass Effect 3 (from the desktop shortcut, if that makes any difference) after logging in to Origin in offline mode with no WiFi connection, and it worked fine. Loaded up my save just fine even though I have extra items from the CE (which Origin seems to treat like DLC) and completed From Ashes on that save.

I think it only authorizes the DLC the first time you play after downloading it. Maybe it checks again whenever you play while online just to be sure.