The reason 200 mcg or 500 mcg are not good doses: If a person malabsorbs severely, they will get very little or nothing from those doses. If a person can absorb normally from B12 in supplement form, but does not have enough stomach acid to break B12 out of food, they would get more from 20 mcg than some would get from 1000.

To be reasonably sure of getting enough B12, 1000 mcg (or more) is best. It is safe, so thank goodness the larger dose is not a problem.

And as Glenn posted, methylcobalamin is a better bet when available.

The repair process can continue for several years.

rose