With all the suplimentation going on limiting it to 400 mcg (NOT mg) is going to be hard.
The key is to limit it to 1,000 mcg/1 mg; above that the symptoms of pernicious anemia (Vitamin B12 problems) can be masked until you've gotten irreversible nerve damage.
Apparently has strong correlation with IQ. Makes me wake up instantly in the morning. Less tired. Better concentration.
Don't take more than ~400mg /day.