The RDA is very low, 3 mcgs or so. Many of us take 1000 mcgs a day. B12 is not absorbed well in the gut. Depending on the dose available at a good price, sometimes I take a 2000 mcg lozenge each day. I usually get the Now brand at VitaCost because it is a good price. I prefer to get the methylcobalamin version, not the cyanocobalamin version.

The healthy blood level of B12 is 370 pm/mL to 960. I keep my levels at the top of the range taking 1000 to 2000 mcgs a day.

Blood levels do not indicate utilization.