The metabolic profile variability of women with diabetes mellitus type 1 (DM1) during breastfeeding, leads to a reassessment in managing glycemia, mainly to prevent hypoglycemia. In this retrospective study we assessed insulin needs, vis-à-vis breastfeeding in DM1. A 10.7% reduction of daily insulin dosage, compared to pre-pregnancy insulin needs, was noted in women who breastfed exclusively versus 10.8% in those who supplemented breastfeeding (p = NS). Women who experienced hypoglycemic episodes, tended (but not significantly) to be younger (p = 0.10), with longer duration of DM1 and more weight gain in pregnancy. Exclusive breastfeeding was associated with younger age (p = 0.04), regardless of hypoglycemia (p = 0.25).