do you know why it would cause hair loss for some in the high doses is it due to depleting other b vitamins. did you notice any hair loss. i do seem to get some thinning from using 500mg HCl a day. i used it alongside, 3.5mg b6 and 150mg magnesium. the other b vitamins like b2 and biotin, b5, i would only supplement once per week. it seems to cause more histamine as well, like more sensitivity to fermented or soured foods or spicy foods... easier to get a runny nose. for now ive reduced it down to 500mg b1 hcl once or twice per week! my daily supplements now have cut back to just 200mg usp caffeine, some policosanol, vitamin d3, and natural dessicated thyroid!Yes, I had that problem. Yes, the high dose thiamine hcl corrected it. If the gut bloating is caused by the lack of gut motility and things are getting stacked up in there then yes thiamine could well be the solution; it was for me. Gut peristalsis (which moves things along) is dependent upon the autonomic nervous system to be functioning. The autonomic nervous system must have thiamine to work.
In addition to peristalsis requiring thiamine to work, thiamine is also needed for adequate stomach acid. If your stomach acid is low (mine was) then things don't get digested properly which messes up the process. Low stomach acid plus no peristalsis is pretty miserable.
I think that I've had a thiamine deficiency for many years. I have a lot of heavy metals in me. I've recently learned that heavy metal (specifically lead) uses up thiamine so you require more. I took Bactrim antibiotic summer of 2020 which just about finished me off because it blocked thiamine function on top of me being thiamine deficient and needing more due to my lead poisoning. The high dose thiamine hcl gave me my life back.