This is Oregon Grape, but it isn’t really a grape. The berries are very sour - too sour to enjoy eating raw, but good for making jams or preserves.
In Latin, it’s called “Berberis aquifolia” and its roots produce berberine which has been used in traditional herbal medicine for a long time to control blood sugar and reduce weight.
There are, of course, common side effects if the dose is too high for the person taking it. Do I think your average healthcare provider can offer insight and useful guidance on this or any other traditional herbal remedy? I don’t really need to answer that, do I?