evidence: A special note on infant formula and breast milk The American Academy of Pediatrics stresses that babies under 6 months of age shouldn't be given any water at all, maintaining that formula or breast milk provides all the hydration they need. While it may seem harmless, practices like diluting formula or breast milk with water can lead to death from water intoxication in infants. That's because their kidneys aren't yet mature, so giving them too much water causes their bodies to go into hyponatremia and disrupt brain function, says Carla Laos, MD of Hazel Health. If you're struggling to afford formula and/or cannot find baby formula, talk to your doctor to see if there are resources available to help you. RELATED: How Much Formula to Feed a Newborn How to Fix Overhydration If your little one truly has taken in too much water and/or you feel they're acting funny, the best course of action is to head straight to the emergency room to get them prompt medical attention. Water intoxication treatment will vary based on how low a baby's sodium levels are.