I have diarrhea about one to two times a week and loose stools about 50% of the time after taking metformin (common medicine for diabetes) since 2006.

Strangely, I do not have the above symptoms whenever I am overseas or when I am off the medicine (trying out other medicine). Can anyone help to explain?

Also, my doctor has advised me to do a colonscopy recently. I am not sure if I needed one. Can anyone give me some advice?

Thank you