I've been vegetarian / vegan for almost 10 years myself and get my vitamin b12 levels checked regularly. A lot of meat eaters actually have low vitamin b12 levels too because of lower intrinsic factor (gut ability to absorb b12) caused by age or distinct genetic setup. Omega 3 is also something I keep in check with 2-3 table spoons of ground flax-seeds a day. Flax oil is a good source of omega 3 as well but much more difficult to handle because it needs to be fresh, cooled and consumed relatively quickly.

Be aware that a vitamin b12 deficiency often happens without symptoms, also meeting the lower threshold of acceptable levels doesn't mean you have got enough of it.

I would advise everyone but especially those on a vegan diet to get their vitamin b12 levels checked regularly. Take your supplements! Don't ruin your brains!

Check out this very informative video by Michael Greger - vegetarian / vegan himself, he has debunked a lot of myths around proper veg diet some 12 years ago (yes the video is pretty long - so what it's your health that is at stake here):

https://www.youtube.com/watch?v=q7KeRwdIH04

Also good books on the topic:

http://www.goodreads.com/book/show/541482.The_New_Becoming_V...

http://www.goodreads.com/book/show/48307.Becoming_Vegan

Don't be a pudding veggie, be informed and healthy!