B-12 plays an important part in the formation of red blood cells, the way your brain and metabolism function as well as the overall health of your GI tract.  Before you take my word for it, check with your physician or nutritionist to see what source of B-12 is right for your body and your needs. If you are a vegan you need to find an adequate supplement because there are no reliable food sources to help you gain B-12.  That being said, you can apparently find B-12 in some nutritional yeasts and fortified cereals, but consistency is key as well as determining if the source of the B-12 is actually vegan.  I have found that the mykind B-12 spray by Garden of Life offers a great tasting spray as well as a convenient way to obtain this essential vitamin.  From what I understand the B's need each other to maximize their effectiveness, so locating a vegan multi is key.  The source of B-12 in this product comes from methylcobalamin which is a compound more readily available for the body to utilize.  The spray comes in a raspberry flavor and is pleasant overall.  I choose to store it in the fridge to keep it cool, and to help remind me to take my daily dose.  I paid $13.99 for it directly at the store, but you can buy directly from Garden of Life if you are interested.  I have not experienced side effects while taking a B-12 supplement, but apparently they can occur so do what is best for you.