Yes, milk production takes a lot of energy, and breast milk is loaded with lactose, a type of sugar. When you nurse your baby, lactose leaves your body, and your blood sugar levels may dip by up to 25%, resulting in hypoglycemia. You need to check your blood sugar more often. It is generally a good idea to have a snack before nursing and to keep some fruit juice nearby while you breastfeed and sip lots of water to stay hydrated.