The safety of using biguanides during pregnancy has not been established. Nor is it known whether these medications are passed to babies during breastfeeding.

Women who are pregnant or may become pregnant should inform their physician. Pregnant women must maintain proper glucose (blood sugar) levels, as high glucose can cause birth defects or excessive weight gain in babies. Many women who use antidiabetic agents are switched to insulin therapy during pregnancy.

Elderly patients are more vulnerable to side effects associated with antidiabetic agents such as biguanides. They are particularly susceptible to experiencing an excessive drop in glucose (blood sugar) known as hypoglycemia. This should not be a major issue for those using biguanides unless they are combined with another antidiabetic agent.