How long does the diarrhea last when first starting metformin?

I started Metformin at 4 x 500mg per day. For a very long time I had days where the explosive and I mean, really, really, really, really, explosive diarrhea kept me for days on and near the toilet. I had the pharmacist and doctor ensure that it was the Mylan (coated/slow release) Metformin and still the problem persists.

Today, I take 1 x 500mg pill after breakfast and 2 x 500mg pills after dinner. Sometimes, once in a while, I have very loose stools. More often, my stools are thicker than toothpaste, but not much. I have started going to the local weight management clinic, and I am using My Fitness Pal on my Android to log the food I eat, and try to remain below 1600 calories per day. The reduced food intake and the increase in vegetable intake along with increased fibre content in what I eat seems to have arrived at a good balance. I am not a heavy exerciser, but at 6 lbs loss per month, I will come to a point where I will be able to take fewer or no pills, provided the weight stays off, for a very long time. I have clearly been given a repreive here and hope to loose around 160 lbs overall and can get off some of the pills, at least for the next 15 years.

So, in response to your question, it could stabilize within a week, but getting your diet in order will help a great deal, as well as discussions with your medical professionals.