thank you to all once again for this very helpful information! I was diagnosed about 6 weeks ago with PN caused by taking an antacid daily for over 10 years and Metformin over the past 18 months. I have had numbness in feet for quite a while, but when I started stumbling and tripping I took notice.

None of the docs diagnosed a b12 deficiency because serum b12 is normal; however, sudden onset of trembling throughout my body, jerking and twitching muscles every time I would stop moving led me to think it may be B12.

I have had 7 k1000 mg doses of the "cyan" type of B12 and 5 1000 mg doses of the "methyl" type (we FINALLY found a local source!). I am also taking 900 mg's of Neurontin daily to control symptoms.

My question is: My muscles are extremely weak and now my doc is suspecting MS. Is profound weakness a side effect of high dose b12 therapy?