The standard medical dose is around 1000mcg each month.

"1,000 mcg daily for 1 week (5-10 days) followed by 1,000 mcg once weekly for 4 weeks and then 1,000 mcg monthly."

IMHO people go over board on B12. I do 1000mcg every week. I notice no difference with ED injections to weekly injections. Just my .02.