For me it was at least a month, maybe 6wks.

First the arms going to sleep at night (some nights) got less and less, and now my hands are better. (I've had carpal tunnel as a primary symptom of my thyroid problems--and it was very very bad during my pregnancy when I was 34. It improved some after delivery..the EMG showed tho it was severe.)

If I do something extreme, like handle heavy rocks, I can feel the zing in my hands. Sewing with a needle is hard for me too.
So I gave up crocheting for example. Heavy digging or twisting with a trowel in the dirt, can also set me off.

I did 300mg of benfotiamine for about two weeks, then reduced to 150 mg daily. Remember I was using regular thiamine before that with some success. I also now use 100mg of r-lipoic acid for insulin resistance control daily.

My carpal seemed mostly due to fluid retention. So I watch my sodium intake, and use a diuretic once or twice a week. Since the benfotiamine, this swelling is very much less. So for people who have this peripheral edema, the benfotiamine seems very useful.