B12 injections are given intramuscularly and  work by increasing your levels of vitamin B12 so that you can make red blood cells that work properly to carry oxygen around your body.    

Areas in which you could benefit include, increased Energy levels, Mental clarity (B12 injections can help with memory, focus, and cognitive function), Mood swings, depression, and loss of focus, sleep, B12 injections can help regulate sleep, promote healthy skin, hair, and nails, help boost the immune system by helping produce white blood cells, which fight infections and weight loss by improving metabolism.