Supplementation started immediately after blood test that was after first symptom that was 4 days after car wreck. Self diagnosed as trauma-induced Neuropathy.Neurosurgeon just said PN. Probably didn't want to tie anything to accident as testimony doesn't pay like doing surgery. Learned later that Metformin use over long time affects B-12 absorbtion in around 30% of diabetics. Good Luck, Ken in Texas.