Prior to 1980 about the only relativly common form of thiamin was thiamin hcl and then most vitamins and enritched food products changed to thiamin mononitrate. While thiamin HCL is a wonderful form of thiamin for 99.99 % of the population for some reason I can't take it. When I take thiamin HCL in a dose dependent mannor I become nurvous and depressed. For example ony taking 2 or 3 mg just has a slight effect but taking a 100 mg tablet and in about 1/2 hr I exhibit symptoms like Parkinsons but in my case just taking some natural B1 cleared up my symptoms in just 30 to 60 min. When I discovered this and startind to avoid all sources of thiamin HCL about 80% of my stutering cleared up.
Then years later came upon a report that large doses of B1 helped about 30% of people who stutter. In this case when it works it works quite rapidly, withen a week or so or simply doesn't work. After a lot of personal experimation I found that thiamin mononitrate at 50 mg 3 times a day reduced my stutering about 98 % . Some how Benfortamine doesn't help me as much on the other hand if I need to do any public speaking I just take 200 mg of Sulbutiamine before doing the talk and I simply never stutter. By the way I also have obstructive sleep apnia and find that taking B1 also decreases the severity of my sleep apnia about 10% .
I wanted to throw this out incase anyone else has an odd reaction to thiamin HCL you may simply need to try another form of this vitamin.