Over the course of 1+ year I have slowly increased my Methyl-B12 dosage from a couple of sublingual tablets a day (1mg each) to 7-8 with some significant improvements. Unfortunately Enzymatic's Infusion B12 lozenges are excessively sugary for my taste and it gets annoying after 3 or 4 of those, let alone 8 or more... I was looking for a higher dose replacement so I tried Source Naturals' 5mg sublingual methyl-B12. They also taste rather sweet. They call it a "natural raspberry flavor"... I wonder if they've ever tasted a real raspberry Anyways for one week I've been taking these tablets instead of the usual Enzys... and unfortunately I have to report that they don't work as effectively. As other people have reported there seem to be a difference in efficacy between brands, be it the active ingredient itself, the speed at which tablets dissolve... who knows... The Source Naturals' 5mg lozenges work, but just not as good the others. In the last three days I've gone back to taking 5x 1mg Enzy tablets in the morning and the effect is clearly different and it wears off more slowly and evenly. Mornings for me are critical as I always have a hard time to get started, clear up my mind and remove the brain fog I am still inclined to use the 5mg tablets for convenience but I will probably need to up the dose to match the effect of the other brand.