needshope78, chemotherapy may have caused magnesium deficiency. Thiamine (B1) requires enzymes created with magnesium and a symptom of deficiency of B1 is neuropathy. Thiamine works best with the other B vitamins. Boron increases magnesium absorption as noted in "nothing boring about boron." To understand more about magnesium search on "krispin magnesium" and also "mgwater". Always consult with your doctor before using any supplement.