Babies can start drinking small amounts of water at 6 months old, once they begin eating solid foods. Before 6 months, breast milk or formula provides all the hydration an infant needs, including water. Both the World Health Organization and the American Academy of Pediatrics align on this timeline.
Why Babies Under 6 Months Don’t Need Water
Breast milk is about 80% water, and infant formula is mixed with water already. Together, these provide enough fluid for growth and for replacing what a baby loses through skin, breathing, stool, and urine. Giving extra water before 6 months can actually cause harm because of how an infant’s body handles fluids.
Young babies have immature kidneys that can’t efficiently flush out large volumes of water. They also have an intense hunger drive that can lead them to fill up on water instead of calorie-rich milk. When too much plain water enters a baby’s system, it dilutes the sodium in the blood, a condition called hyponatremia. According to CDC case reports, symptoms begin when sodium drops sharply and total body water increases by 7% to 8% or more. This causes cells in the brain to swell, which can lead to seizures, loss of consciousness, and in rare cases, death.
The WHO’s Baby-Friendly Hospital Initiative is explicit on this point: babies should not be given additional food or drink, including water, unless medically necessary.
Signs of Water Intoxication in Infants
Water intoxication is uncommon, but it can happen quickly in a small baby. Early signs include nausea, vomiting, a bloated stomach, drowsiness, and irritability. The baby may seem unusually fussy or lethargic in a way that doesn’t match their normal behavior. Severe cases can progress to confusion, seizures, and coma. If you notice any combination of these signs after a baby has consumed water (or overly diluted formula), seek medical help immediately.
The most common cause historically has been tap water given as a supplemental feeding or formula that was stretched with extra water to make it last longer. Juices, sodas, and teas have also been linked to infant water intoxication.
How Much Water at 6 to 12 Months
Once your baby starts solids around 6 months, you can introduce water in small amounts. The CDC recommends 4 to 8 ounces per day for babies between 6 and 12 months. That’s roughly half a cup to one cup total across the whole day, not per meal.
At this stage, water is a complement to breast milk or formula, not a replacement. Milk still provides most of a baby’s calories and nutrition. A few sips of water with meals helps babies get used to drinking from a cup, keeps things moving through their digestive system, and helps wash food residue off emerging teeth. You don’t need to push water if your baby isn’t interested. Offer it, and let them take what they want.
Water Intake After 12 Months
Between 12 and 24 months, the recommended water intake jumps to 8 to 32 ounces per day (1 to 4 cups). By this age, toddlers are eating a wider variety of solid foods and may be transitioning off formula entirely. Water and plain whole milk become the primary drinks. The range is wide because activity level, climate, and how much water-rich food a child eats (fruits, soups, yogurt) all affect how much they need to drink.
Do You Need to Boil the Water?
For babies over 6 months, tap water generally does not need to be boiled before offering it as a drink. For babies under 6 months who are formula-fed, the NHS notes that small sips of cooled boiled water may be appropriate during very hot weather alongside their regular feeds. If you’re mixing powdered formula, follow the instructions on the label regarding water temperature and preparation.
One thing worth knowing: if your tap water is fluoridated, reconstituting powdered formula with it can expose your baby to fluoride levels between 0.64 and 1.07 parts per million, which is higher than the fluoride in ready-to-feed formulas (around 0.15 to 0.21 ppm). Communities have been adjusting fluoride levels down to 0.7 ppm, which reduces the risk of mild dental fluorosis (faint white spots on developing teeth). If this concerns you, alternating between fluoridated tap water and low-fluoride bottled water for mixing formula is a reasonable approach.
What About Constipation in Young Babies?
Constipation is one situation where a small amount of water might be offered before 6 months. The Mayo Clinic suggests that for babies 1 month and older who are constipated, a small amount of water can help soften stool. This means a few sips, not ounces, and it’s best to check with your pediatrician on exactly how much. Water is typically the first thing to try before fruit juice.
Practical Tips for Introducing Water
When your baby hits 6 months and starts solids, offer water in an open cup or a straw cup rather than a bottle. This helps develop oral motor skills and makes the eventual transition away from bottles easier. You don’t need to buy special “nursery water” unless your tap water quality is a concern.
Keep it plain. Avoid flavoring water with juice, sugar, or honey (honey is unsafe for babies under 12 months). Don’t offer sparkling water, sports drinks, or flavored waters. At this age, the goal is simple: get your baby comfortable with the taste and feel of plain water alongside their meals, while breast milk or formula continues to do the heavy nutritional lifting.