Cyanocobalamin is a man-made form of vitamin B12 used to treat low levels (deficiency) of this vitamin. Vitamin B12 helps your body use fat and carbohydrates for energy and make new protein. It is also important for normal blood, cells, and nerves. Most people get enough vitamin B12 in their diet, but a deficiency may occur in certain health conditions (e.g., poor nutrition, stomach/intestinal problems, infection, cancer). Serious vitamin B12 deficiency may result in anemia, stomach problems, and nerve damage.