hey there JS
all right so pharma's not why your 1,25 is high. good to know.
B12 is a single test. just serum cobalamin. easy
researchers have studied b12 and cognitive function in all kinds of things like alzheimer's, senile dementia, down to impaired cog function in vegan or vegetarian adolescents, eg
Signs of impaired cognitive function in adolescents with marginal cobalamin statushttp://www.ajcn.org/content/72/3/762.short
mind you many other things are involved in optimal cognitive function too, so if there's something cognitive going on with you, you might be wise to cast a broader investigative net
for just one example, zinc has been a problem for me in the past, eg gave me some difficulty assessing distances and relative speed etc.
as for why your 25(OH)D3 is low, i would hypothesize that you're not processing your 4000IU d3 optimally, quite likely due to absent complementary mineral supplementation. personally when i took 4000IU d3 for a long time, first i noticed that i had no magnesium left in my system, and a pharmacist set me straight re timing of intakes. i'll tell you more if you want to hear it. next i noticed that i had no zinc left in my system. it wasn't all the d3's fault- i had a stupid diet for years prior - but it tipped me over the edge as far as those other important minerals went.
curious if you would be able to get calcium, magnesium, and zinc tested? that could help you decide what kind of mineral boost is needed and for how long, then re-measure minerals and the d3 metabolites, and then re-introduce d3 supplementation, with modifications to amounts if needed.
if you just want to get a cal-mag-zinc blend and see what happens, that's an option too
but if symptoms don't clear, it's hard to tell without testing whether you need to eat more mineral-rich foods and/or take more supplements and epsom salts baths, or look for a different solution.
anyway that's all for now