Vitamin B12 / Cyanocobalamin / methylcobalamin is a synthetic (man-made) form of vitamin B12. Naturally occurring vitamin B12 is found in fish, seafood, milk, egg yolk and fermented cheeses. Vitamin B12 is essential to the development of healthy blood cells, nerve cells, and proteins in the body and for the normal metabolism of fats and carbohydrates in the body. Lack of vitamin B12 can result in anemia, stomach problems, and nerve damage. Cyanocobalamin treats or prevents vitamin B12 deficiency and a resulting type of anemia, called pernicious anemia.