It's important that you figure out how much milk your baby will need while you are gone. Often care providers are not aware that breastfed babies need far fewer ounces of breast milk than the typical amount of formula that babies need. Your breast milk changes as your baby grows, making it a very efficient food. A full supply of breast milk is approximately 30 ounces for 24 hours. By figuring out how many times in 24 hours your baby eats and dividing 30 ounces by this number of meals, you’ll have a good idea of how many ounces your baby takes per feeding. Then consider how many feedings she'll have while you're apart, and this will give you an idea of the amount of milk you'll need to leave.