If you have a deficiency, it will make a difference in your energy level and possibly in your appetite. If not, you will piss out what isn't needed. You cannot build up supraphysiological levels of b-12. If you are interested in seeing how b12 effects you, without investing in the injectable, I've read that sublingual works almost as well. The issue with b12 is, its hard to absorb orally...more for some than others, and more for people who are older. thats why the injectable is popular but with a sublingual, its being taken directly into the blood through the thin skin under your tounge and you can raise your levels to normal via this method. For an injectable, the dose is 1000mcg. I've read that you can get a similar effect with 5000mcg of the sublingual. I've also heard of people using a combo of the both. 1000mcg injectable, 1x wk, followed by 5000mcg sublingual every day