Good advice from Andbreathe. Yes Metformin doesn't work or kick in instantly, instead it usually takes a couple of weeks before it becomes fully effective.
Though Metformin has become a first choice medication for controlling Type 2 diabetes and is proven a good medication in controlling diabetes blood glucose levels, in the initial stages of taking Metformin you must be aware that your body might react somewhat against this medication and produce a few side effect that aren't very pleasant.
Not everyone experiences these initial side effect and I hope that you will be one of those that fall into this category, but do continue even if they occur, bearing in mind that a SLOW RELEASE version of Metformin is also available should this be the case.