Remember you are making a major change in your eating. That could be causing you to be tired. When I became vegan about 14 years ago I lost about 21 pounds in about two weeks. I felt so much better but I was not tired. I had to learn how to make the transition. Now I use Silk on my cereal, Nanonase on sandwiches, and other substitutes. I also eat much more variety that I did as a flesh eater. Being vegan is great!