This drug should be stopped about 2-3 days prior to dye studies. My mother has been taking glucophage for the last six months and has experienced bouts with diarrhea. I have heard stories of heart attacks. Her dosage is 850 mg, twice per day. If it is episodic, I doubt the glucophage is involved.
Patients do experience diabetic enteropathy, which is manifested by diarrhea.
Clonidine usually fixes this. Heart Attacks are common in diabetics, but glucophage has not been implicated yet. Her dosage is about average. Metformin unlike the sulfonyureas, will not produce hypoglycaemia. For practical purposes, one drink shouldn't be a big deal if you monitor your glucose.