Human milk is recommended for infants throughout at least the first year of life. Breastfeeding is also recommended for infants of women with preexisting diabetes or gestational diabetes. Dietary Reference Intakes (DRIs) 2002 provides recommendations for energy and macronutrients for all ages and for pregnancy and lactation. During the first 6 months, infants receive an average of 500 kcal/d from human milk, and during the second 6 months 400 kcal/d. To cover this need for the first 6 months of lactation, women need an additional energy intake of 330 kcal/d plus the approximately 170 kcal/d that is supplied by the women's tissue stores, and for the second 6 months 400 kcal/d. The DRIs also set recommended levels for both the infant and mother for carbohydrate, protein, and fats. Women with type 1 diabetes may have problems initiating breastfeeding, and with hypo- and hyperglycemia during lactation. Breastfeeding may have long-term beneficial effects on glycemia in women with gestational diabetes. More research is needed on all aspects of lactation in women with diabetes.