ARI Publication 40 – 2013 Version

Forms of vitamin B6
There are six different forms of vitamin B6, including three unphosphated forms and their
corresponding phosphated forms. All forms can be converted to one another, and should result in
increases in the active forms {PLP and (for a few reactions) PMP).
The six forms of vitamin B6 are:
Pyridoxine (PN)
& Pyridoxine 5-Phosphate (PNP)
Pyridoxal {PL)
& Pyridoxal 5-Phosphate {PLP)
Pyridoxamine (PM) and Pyridoxamine 5-Phosphate (PMP)

ARI survey data reports a slightly higher rate of adverse effects for PLP (11%) than for other forms
of B6 (8%, or 4% if given with Mg). Analysis of their survey data suggests that some children do
better on unphosphated forms (pyridoxine HCL), and some do better on the phosphated forms
(PLP). Both forms should be well absorbed and have similar effects.
So, we suggest first starting with pyridoxine HCL; if it is not effective, consider switching to
PLP. All research studies to date have only investigated high-dose pyridoxine HCL for autism, and
none have involved high-dose PLP

ARI Survey of Parent Ratings of Treatment Efficacy:

%Worse% No Change% BetterNumber of Reports
Vitamin B6 (pyridoxine HCI)8%63%30%620
Vitamin B6 with Magnesium4%46%49%7256
PSP (Vit. B6)11%40%48%920

Safety: High dose B6 should always be taken with magnesium to prevent possible hyperactivity
(which occurs in about 20% of cases when high dose B6 is taken without magnesium).
High dose supplementation of vitamin B6 with Mg in children and adults with autism appears to be
very safe.
In very rare cases (less than 1 in 1000) high dose vitamin B6 can cause temporary numbness in
fingers and toes. Stopping supplementation generally results in full recovery.

For more info: A summary of vitamin B6 studies in autism is available at