I confess that I was part of a group who found the Jarrow's brand methylcobalamin sublinguals to be
ineffective at a point.
I now believe it was my own condition, and not the product that was causing my symptoms.
After stopping Jarrow's, I took AOR brand, 15mg., then later , Solgar 5 mg. They were great, but I began to have a return of paresthesia and vertigo/ dizziness .
It was something other than low B12 that was causing the symptoms. B12 helped for a time. Now I take a low dose B complex.
Other folks may have viable opinions.