Excess vitamin B6 can cause peripheral neuropathy. Recommended daily B6 intake is 1 - 3mg, but some magnesium supplements and sports drinks contain much more. I took the same magnesium brand every day for years, never noticing they included 60mg of B6, and not knowing that excess B6 was harmful.

Blood tests after I got PMR came back with a warning about my high risk for peripheral neuropathy because I had dangerously high B6 levels. The pathology report said the most usual sources of excess B6 were magnesium supplements and sports drinks. I now take a different brand without B6 and blood levels are normal. Food items and all supplements should be checked to see if they contain B6.