I was told I was allergic to metformin because of bathroom issues and was taken off it.

Me too... It's bad for about hours after I take it.

yes rotten egg and lots of gas

I read in some patient reviews that for many it causes horrible sulphur like belching. So that is not unusual. I hated the drug. It made me so sick!

Metformin was a really really bad medication for me. I don't mean to sound gross but it got to the point to where I could not hold my bowels. I mean absolutely cannot hold them. So after many months of ignoring the issue I finally talked to my doctor and was taken off the medication. Sending love and prayers your way