A 6-month-old can start drinking small amounts of water, but only 4 to 8 ounces per day. That’s roughly half a cup to one cup total, spread across the day. Before 6 months, babies don’t need water at all because breast milk (which is 87% water) and formula provide all the hydration they need.
Why the Limit Is So Low
A 6-month-old’s stomach is small, and their kidneys are still maturing. Water fills them up without providing any calories or nutrients, which means every ounce of water can displace an ounce of breast milk or formula they actually need for growth. At this age, milk feedings remain the primary source of nutrition and hydration. Water is a supplement to solid foods, not a replacement for anything.
The 4 to 8 ounce range from the CDC applies to the entire period from 6 to 12 months. Most pediatricians suggest starting at the lower end, around 4 ounces, and gradually offering a bit more as your baby eats more solid food and approaches their first birthday.
When and How to Offer Water
The easiest approach is to offer a few sips of water during meals. When your baby sits down for solid foods, place a small cup nearby. This builds the habit of drinking water with food and keeps the volume naturally low since babies this age take only tiny sips at a time.
Six months is also the recommended time to introduce a sippy cup or an open cup with handles. You can start by showing your baby how to drink from it, then gently bringing it to their lips. Some babies take to a cup immediately, others need weeks of practice. If your baby turns their head away, they’re done. There’s no need to push it. Swapping in a cup for one feeding per day and slowly increasing from there works well for most families.
The Risk of Too Much Water
Giving a young infant too much water can cause a dangerous condition called water intoxication. It happens when excess water dilutes the sodium in a baby’s blood, and symptoms include unusual irritability or sleepiness, low body temperature, facial swelling, and in serious cases, seizures. These symptoms appear when total body water increases by roughly 7% to 8% or more. Because infants are so small, it doesn’t take much extra water to reach that threshold.
For the same reason, you should never water down formula. Adding extra water to stretch a container means your baby gets fewer calories and nutrients per feeding. Over time, this can slow growth. Always follow the mixing instructions on the formula label exactly.
What About Tap Water vs. Bottled Water?
In most communities, regular tap water is perfectly fine for a 6-month-old. You don’t need to buy bottled water unless there’s a known contamination issue with your local supply. In fact, bottled water has a downside: it typically doesn’t contain fluoride, which supports developing teeth.
If your home uses well water, have it tested for nitrates before giving it to any infant under one year. And if there’s ever a boil-water advisory in your area, boil the water for about one minute and let it cool completely before offering it. Keep in mind that boiling kills germs but doesn’t remove lead or other chemical contaminants.
How to Tell Your Baby Is Well Hydrated
You don’t need to track ounces precisely. The most reliable indicator is wet diapers. A well-hydrated baby produces several wet diapers throughout the day. If you notice significantly fewer wet diapers than usual, that’s worth paying attention to.
Other signs of dehydration in a baby include sunken eyes, few or no tears when crying, unusual drowsiness or irritability, and a sunken soft spot on top of the head. The soft spot, or fontanelle, normally feels flat or very slightly curved. If it looks noticeably sunken, your baby likely needs fluids and prompt medical attention.
Breast Milk and Formula Still Come First
At 6 months, solid foods and water are extras. Breast milk or formula remains the cornerstone of your baby’s diet through at least the first year. Breast milk is 87% water, 7% carbohydrate, 4% fat, and 1% protein, so it handles both hydration and nutrition in a single feeding. Formula is similarly designed to meet all of a baby’s fluid needs when prepared correctly.
Think of the 4 to 8 ounces of water as a companion to solid food, not as a hydration strategy. A few sips with meals, offered in a small cup, is all your baby needs at this stage.