Your levels were not in that low 150-300 range... so 5mg may not be needed. I only recommend 5mg for about 3 months or so until the next testing...to see if levels are coming up properly.

There are a few people on PN who continue with it at 5mg. But I don't. Once I had my testing on the Puritan's version, I dropped to twice a week, 5mg.

It takes a while for the liver to store up new reserves, and the
spinal fluid takes some when low. Once those two depots are filled, taking more is not really necessary for long periods IMO.
(unless you have some rare trancobalamin issue, suggesting poor transport etc, but testing for this is still very new and not well understood- or some other rare issue that at this time is not explainable.)

The 5mg is to jump start repair, and replenish long used up stores. But once that is accomplished, 1mg a day would be close to the RDA for a vegan. Testing is really necessary to see where you are in the future to decide completely.