In general, it's not a good idea to give your baby water until he or she is about 6 months old. Until then, your baby will get all the hydration he or she needs from breast milk or formula, even in hot weather.
Giving a baby younger than 6 months oldtoo much water can interfere with his or her body's ability to absorb the nutrients in breast milk or formula. It can also cause your baby's tummy to feel full, which curbs the desire to eat.
While small sips of water probably won't hurt your baby, it's best to check with his or her doctor beforehand during these first six months.
In rare cases, a baby who drinks too much water can develop a condition known as water intoxication, which can cause seizures and even a coma. Water intoxication happens when too much water dilutes the concentration of sodium in the body, upsetting the electrolyte balance and causing tissues to swell.
Adding too much water to your baby's formula not only risks water intoxication, it means that your baby is taking in fewer nutrients than he or she needs. Carefully follow the package directions for mixing powdered or concentrated formula and don't try to stretch formula by using more than the recommended amount of water.
In some instances – if your baby has gastroenteritis, for example – the doctor might advise you to give an electrolyte drink like Pedialyte or Infalyte to help prevent dehydration.
Once your baby is 6 months old, it's okay to give sips of water. You still don't want to overdo it, though, or you might give him or her a tummy ache or make your baby too full to eat well. After the first birthday, when your baby's eating solids and drinking whole milk, you can let him or her drink as much water as he or she likes.