You can start giving your baby small sips of water at 6 months old, when they begin eating solid foods. Before 6 months, babies get all the hydration they need from breast milk or formula, and offering water earlier than that can cause real harm. The CDC recommends 4 to 8 ounces of water per day for babies between 6 and 12 months.
Why Babies Under 6 Months Shouldn’t Have Water
Both the World Health Organization and the CDC are clear on this point: infants should receive only breast milk or formula for the first six months of life, with no other foods or liquids, including water. This isn’t just a preference. There are concrete physiological reasons behind it.
A young infant’s kidneys are still developing and can’t process extra water efficiently. When a baby under 6 months drinks water, it dilutes the sodium levels in their blood. In serious cases, this leads to a condition called water intoxication, where the rapid drop in sodium causes cells in the brain to swell. Symptoms include unusual irritability or sleepiness, low body temperature, facial swelling, and in severe cases, seizures. The CDC has documented cases of infant seizures linked to as little as a few ounces of water given regularly to very young babies.
There’s also a nutritional cost. Water fills a baby’s stomach without providing any calories or nutrients, which means they nurse or bottle-feed less. For newborns especially, this can contribute to jaundice and slow weight gain during a critical growth period. In breastfeeding mothers, reduced feeding also slows milk production, creating a cycle where the baby gets even less of what they actually need.
What About Hot Weather?
Many parents worry about dehydration during summer heat, and it’s a reasonable concern. But for babies under 6 months, the answer is still not water. Breast milk is roughly 80% water and adjusts its composition based on how frequently a baby feeds. During hot weather, breastfed babies simply need more frequent feeds. Formula-fed babies can be offered their usual formula more often. Neither group needs supplemental water before 6 months, even during a heatwave.
How Much Water at 6 to 12 Months
Once your baby starts solid foods around 6 months, you can introduce water alongside meals. The recommended amount is 4 to 8 ounces per day, which is roughly half a cup to one cup total. This isn’t meant to replace breast milk or formula. It’s a small supplement to help with digestion as your baby adjusts to solid food, and it gets them used to drinking water as part of their routine.
You don’t need to push your baby to finish a certain amount. Offer a few sips with meals and let them take what they want. Breast milk or formula should still be the primary source of hydration and nutrition throughout the entire first year.
Best Cups for First Water Sips
Six months is also a good time to start practicing with a cup, and water is the ideal liquid to practice with since spills are no big deal. You have a few good options:
- Open cup: A small open cup helps your baby develop fine motor skills and coordination. The goal is for them to be comfortable drinking from an open cup around their first birthday.
- Straw cup with a lid: A lidded cup with a straw teaches a new sucking motion that’s different from breast or bottle, which builds more advanced drinking skills.
- Spoutless sippy cup: If you prefer a sippy cup, choose one without a spout. Traditional spouted sippy cups use the same sucking motion as a bottle, so they don’t actually help your baby learn new skills.
Whichever cup you choose, the transition away from bottles should be well underway by 12 months. Starting cup practice early with water makes that shift easier when the time comes.
Water Needs After 12 Months
After your baby’s first birthday, water becomes a regular part of their diet. Most toddlers between 12 and 24 months need about 1 to 4 cups of water per day, depending on their size, activity level, and how much milk they’re still drinking. At this stage, whole milk replaces formula, and water replaces much of the additional fluid they were getting from breast milk or formula feeds.
Stick with plain water. Juice, flavored water, and sweetened drinks add sugar without meaningful nutrition, and they can set up taste preferences that are hard to undo later. If your toddler resists plain water, offering it consistently with meals and snacks is usually enough. Most kids accept it once it becomes part of the routine.