I just found one under my microwave that freaked me out. Thats how I found this website. I actually take it and coundnt identify it! I have only Taken it for a month but after I found this post I went to the medicine cabniet and sure enough. Round white tablet imprinted 397 is 500 mg metformin, a drug that treats type 2 diabetes.
Never take someones word for it. I would just toss in down the toilet, Thats my advice anyway.