I have had very high serum Vit B6 too (250) for over 8 years at least but take absolutely no Vit B6 supplements in any form.

I have MECFS and thought that caused my peripheral neuropathy.

I have discovered a 2019 paper by Chelban et al (PDXK Mutations Cause Polyneuropathy Responsive to Pyridoxal 50-Phosphate Supplementation)

The paper suggests that some people have mutations that stop the conversion of vitamin B6 into its active form, pyridoxal 5'-phosphate (PLP).

Sometimes the situation can be rescued with PLP supplementation.

So, I may have loads of the WRONG SORT of Vit B6 floating around in my blood and still have a B6 deficiency (!!)

I'll check with my doctor first - but might try the PLP supplements.

The Google AI says: 'These supplements are used to treat specific conditions, such as certain types of seizures, where the body cannot convert other forms of vitamin B6 into the active form. Unlike typical vitamin B6 supplements (like pyridoxine), PLP supplements directly provide the active vitamin, which may be necessary for those with certain enzyme deficiencies. However, PLP supplements are used less frequently than pyridoxine and are primarily prescribed under medical supervision due to potential side effects like liver toxicity with long-term use.'