Metformin Manufactures

Has anyone found a difference between side effects of Metformin when it is a different manufactures. For a long time mine have been made by Almus and I have always had 'the runs'........a few months ago I went to a different chemist and I noticed it was a different box but did not think much about it, over the next couple of months I did notice my bowel habits had calmed down. Now I have gone back to Boots and again it is Almus manufacturer and my problems have started again. Could it just be coincidence or does anyone think it could be the change in manufacturer. I did read somewhere that sometimes even the coating on tablets can make a differenct. I am not due my repeat prescription for a while yet but if I thought it could be this I would ask my doctor to give me early and try another chemist.

Thanks for any advice.