Is it possible that my 500mg one time a day ER Metformin could be causing weight gain or my Celexa only 5mg amount be causing it either? I am trying to get to the bottom of why all of sudden my weight has increased in the last 2 months. I have insulin resistance and impaired glucose tolerance that is why i use Metformin for prediabeties but am wondering if i should stop since my obesity is already a problem and I am gaining more weight after starting these two meds.