Thanks @JasonUT. Did you get any benefit? How long did it take you to get normal test results? My doctor tried to order a thiamine test for me before I embarked on my experiment but this was refused so I'm flying blind and have only my symptoms to go by. Maybe I should try telling them I've been overdosing and therefore urgently need a test now This strategy did work for a magnesium test once Has anybody here been able to judge just from symptoms when/if they can reduce their dose? How?