If you are very low in B6, from poor diet, or some other reason,
you will get neuropathy. And if you take too much...and really almost all the reports are in the 500mg-gram level, you will get nerve toxicity.

This is the only vitamin that causes neuropathy on both ends of the dose range. We had a poster here not too long ago who had low B6 serum test. And we have had a few with very mild intake doses --below 50mg who had symptoms too.

I have a B6 thread on Vitamin forum:
http://neurotalk.psychcentral.com/thread30724.html

B6, folate and B12 all work to repair nerves. They also reduce homocysteine levels in the blood which when high are thought to cause damage to the blood vessels and heart attacks/strokes.

B6 can help carpal tunnel.. this is when 10 yrs ago I discovered the active form called P5P and started posting about it on the net (at one time I had very severe carpal tunnel). Now P5P is being investigated to reduce risk of heart disease by a big pharmaceutical firm, who wants to take all P5P off the shelves as OTC..so they will make more $$ from it.

B6 does many things in the body...runs the muscles, and also makes serotonin in the brain...along with hundreds of other things. B6 is activated by an enzyme that uses riboflavin B2. Some drugs and genetic failures will prevent this conversion as well.