What should I know about metformin before taking it?

Metformin can cause a rare but sometimes fatal condition called lactic acidosis. This is more common in people with kidney, liver or heart problems. People who drink excessive amounts of alcohol or are elderly may be at higher risk. Your doctor will advise you on a healthy diet and exercise plan to follow in addition to taking metformin. Let your doctor know if you are pregnant, plan to become pregnant or are breastfeeding. Research has shown metformin to be not harmful to the fetus in pregnant women, but it is not usually used during pregnancy. It is unknown if metformin can be passed through breast milk, so tell your doctor if you are breastfeeding because many drugs can pass from mother to child in this manner.