Do you have any idea what would cause the inability utilize thiamine?
I know someone who has had multiple TIAs & has "ataxia, numbness, neuropathy". They thought it was ALS & are now testing for MELAS
People with intestinal issues do not absorb thiamine well and even if their blood levels are normal they still benefit from extra thiamine. Some people also cannot convert thiamine Hcl from diet/supplement to the active form TPP, as that depends on ATP synthesis. So, in that case taking thiamine with niacinamide, methylene blue, thyroid, etc may help convert it into the active form.