I'm prediabetic, well I was the last time I was tested. I've tried berberine, and it did nothing to lower my blood sugar readings. I've also tried chromium, cinnamon, moringa, but none of them worked. I'm always looking for a magic bullet, but I don't think there is one out there. The solution is eating meat, fish, eggs, cheese, served with vegetables that grow above the ground, and cutting out carbs, Lots of people seem to think that eating oats is OK, but even a small amount sends up my readings, and so do lentils and beans.
I've read that Vanadium is supposedly good for lowering BG levels, but this is not one I've tried. I'm giving this one a miss until I hear from good sources that it works.
Good luck in your search.