What should I avoid while taking metformin?

You should avoid excessive amounts of alcohol if you are taking metformin. Alcohol can increase the risk of side effects and may contribute to the risk of a rare but extremely serious condition called lactic acidosis. Avoid other medications that are known to be toxic to the kidneys. If you are thinking of becoming pregnant or are pregnant, talk to your doctor before taking this drug. Avoid breastfeeding and talk to your doctor, as while it has not been proven that metformin is found in breast milk, many drugs can be passed from mother to child in this manner.