Benfotiamine is extremely beneficial in glucose metabolism. There definitely may be a link if you take it regularly. It does help with SFN pain for sure. Did you take Benfotiamine the morning of the OGTT?

My personal experience is that Benfotiamine is very good at reducing blood sugar levels. My personal fasting levels reduced by about 10 points on a dose of 500 mg a day. For me its been a win/win, I have never been below 70 even at my lowest reading. Usually i average in the low 80s.

Do you have any idea of your levels before you started taking the benfotiamine? A1C, fasting or OGTT? Personally i wouldn't stress over anything unless I had a really low A1C level. Because that shows what your blood sugar level is as an average over 3 months. If you have been taking Benfotiamine for that time it would be a really good gauge. If you had a normal fasting it seems like this is really not a cause for concern. My doctors have done all 3 blood sugar tests several times. What the told me was that they need to see a trend across all the tests to make any serious diagnosis.

You could always do blood glucose monitoring at home as well. Can get a kit pretty cheaply on Amazon. Its a good way to see what may be a trigger on your own without dealing with doctors visits and lab workups.