Is the B12 methyl type or cyano? Cyano is synthetic and some people cannot tolerate it or activate it.

I have never seen anyone get more symptoms from those you list. However, rose, who used to post here claimed that people who start with B12 who were very low to start, often get temporary painful symptoms when they start to heal.

I know when I started my thyroid medication, my feet had gone pretty numb by then. I had been hypo most of my adult life.
The whole first year on the levothyroxine, and my feet "woke up" and tingled/burned for a long time until they were back to normal. This is like when you get very cold hands out in the snow, and warm up....you get red and tingle/burn....it was like that only 24/7 for a year! That didn't involve ANY vitamins, as I didn't have the training yet for that and wasn't doing supplements yet. (this was almost 20 yrs ago). But it does illustrate the concept of healing and odd sensations, that rose claimed she had while improving her combined degeneration of the spinal cord with B12.