It says:
"In a preliminary trial, 2,500–5,000 mcg of vitamin B12, given by injection every two to three days, led to improvement in 50–80% of a group of people with chronic fatigue syndrome (CFS), with most improvement appearing after several weeks of vitamin B12 shots."
I use 1000mcg/ED, but only when cycling.. I never noticed any increase in appetite or energy, if thats what you are looking for it to do.. Some people notice it, some do not..