You don’t need to give your baby water until they’re 6 months old. They get all the hydration they need from breastmilk or formula milk. Having water earlier than that could put them at risk of water intoxication.

Your little one — if under 6 months old — receives both nutrition and hydration from breast milk or formula, not water.

This is because babies’ bodies aren’t suited for water until several months after birth. Tiny tummies and developing kidneys put them at risk for both nutrient loss and water intoxication.

Baby tummies are quite small. In fact, at birth, a baby’s belly only holds about 1 to 2 teaspoons, or 5 to 10 milliliters (mL). This is why the baby needs so many feedings in a 24-hour period.

Baby’s tummy does grow over the first 6 months of life, but it’s pretty gradual. By the time they’re 1 month old, their stomach capacity is about 2.7 to 5 ounces (80 to 150 mL). By 6 months — when you can introduce little sips of water — they can generally hold about 7 ounces (207 mL) at a time.

The Centers for Disease Control and Prevention (CDC) recommends giving babies 4 to 8 ounces (oz) of water when they are 6 months old.

When can the baby have water?

At around 6 months of age, it’s OK to introduce small amounts of water — we’re talking on the teaspoon or tablespoon scale, not the full-bottle scale.

It’s a good time to start introducing the concept that thirst can be quenched with water, but your baby’s main source of hydration (not to mention nutrition) should continue to be breast milk or formula.

Caution

Even between 6 months and 1 year of age, the amount of water you give your baby should be very limited. It’s more for them to get the taste and experience of water rather than for any real medical purpose, like hydration.

Formula and breast milk are very hydrating and also give your little one what they need to grow and thrive.

Another very serious risk of giving babies water before they’re ready is water intoxication.

When the kidneys are given more water than they can handle, the excess water ends up in the bloodstream. This dilutes the fluid in your bloodstream and lowers the concentration of important electrolytes, like sodium. Too much dilution and you’re at risk for hyponatremia, which literally means too little (hypo) salt in the blood (natremia).

Baby kidneys can’t handle as much water as adult kidneys. In addition to being much smaller than an adult’s kidneys, a baby’s kidneys are also not as developed. So they can’t process as much water at a time.

So, giving a baby younger than 6 months even a moderate amount of water in a short period of time can lead to hyponatremia, which, at its most dangerous, can cause brain swelling and even death.

In fact, because the brain is still developing as well, the swelling can happen more easily in an infant with hyponatremia than in an adult with hyponatremia.

Talk with a pediatrician or primary care doctor if you have any concerns about your baby’s hydration or readiness for water. Your timeline for introducing water may vary depending on whether your baby was born prematurely or has certain health conditions.

In addition, if your baby shows any of these signs of water intoxication, head to the hospital immediately:

  • inconsolable crying
  • vomiting
  • lethargy
  • seizures
  • tremors

Once they’re 6 months old, babies can usually have some water, typically about 4 to 8 oz. However, having water earlier can increase their risk of water intoxication, as their kidneys are not developed enough to filter it.

Adding too much water to formula milk can also deplete it of essential nutrients that your baby needs.