Hello,

        The Compendium of Pharmaceutical Specialities (Canadian
"Physician's
Desk Reference") states that "Metformin, at therapeutic doses, does not
cause hypoglycemia when used alone in man or in the nondiabetic animal,
except when using near lethal dose.  Metformin has no effects on the
pancreatic beta cells".  Also, "the plasma concentration at steady state
ranges about 1 to 2 micrograms/ml".  We do not know the milk:plasma
ratio, but if it is near 1, and given the above information, it seems
that metformin should not be contraindicated in breastfeeding women.  Of
course, the mother could always take insulin.  If she really wants to
continue breastfeeding, this should be offered as an option.

Jack Newman, MD, FRCPC