Metformin is torture, for some people.

What it does is increase the activity of serotonin receptors in the gut, which increase motility. It has also been shown recently in one study to increase gall bladder contractions which for some patients is an additional torture.

Your options are to ask your doctor for extended release form, which may help or not. The original Glucophage ER did not work for me either.

There is a newer version, called Glumetza, which worked for me for several months, and then the torture returned! This form does not have a generic and releases the drug more slowly than the original ER forum did.

You should have blood work on your kidneys periodically to make sure the drug is being cleared properly and not building up in your system, as well.

I personally believe based on my own experience with Metformin, that some people just cannot tolerate it in any form.
It remains very good when tolerated GI wise however.

In my case the gall bladder effects just became too much for me!