It may be that you are a rare person who is sensitive to something in the preparation. But, it is important to recognize that symptoms can worsen temporary as improvement takes place. That is especially common after a period of easy improvement during which time symptoms look like they are just going to go away quickly and easily. Those who have significant damage to repair often find that symptoms worsen as a particular system or area is being worked on.

Anyway, you probably took B12 long enough to build stores, and unless you store exceptionally badly you will continue to benefit from those stores for a very long time. However, not good to take that for granted.

I am glad that since you can get the methylcobalamin form you will.

rose