I took it for a short spell with such a small difference to blood glucose that I could not say definitely whether it had contributed or not. But I have recently gone back onto it for a non-diabetes health issue for which it has proved positively beneficial. If my experience is typical, it needs to be taken for some time before a definite benefit can be seen - in my third month of taking it I am still seeing small improvements, so I shall continue.
There are many different options and I take one that is free from any additives or fillers, therefore has to be kept refrigerated and is a little more expensive, so do your research if you want to try it. We definitely get what we pay for in terms of quality.