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. Between 6 and 12 months, the CDC recommends limiting water to 4 to 8 ounces per day.
Why Babies Under 6 Months Shouldn’t Have Water
A newborn’s kidneys are still immature and can’t efficiently process extra water. When a young infant takes in too much water, it dilutes the sodium in their blood, a condition called water intoxication. Sodium levels drop rapidly, causing cells throughout the body to swell. In the brain, that swelling increases pressure and disrupts normal function.
Two factors make babies under 6 months especially vulnerable. First, their kidneys simply aren’t developed enough to flush excess water the way an older child’s can. Second, the powerful hunger drive of early infancy means a baby may eagerly drink water from a bottle without any ability to self-regulate. Symptoms of water intoxication in infants include irritability, drowsiness, nausea, vomiting, and a bloated stomach. In severe cases, it can progress to seizures or loss of consciousness.
This also means you should avoid diluting formula with extra water to stretch it. Formula mixed according to package directions already contains the right balance of water and nutrients.
How Much Water From 6 to 12 Months
Once your baby starts solid foods around 6 months, you can introduce water in small amounts. The target is 4 to 8 ounces spread across the entire day. That’s roughly half a cup to one cup total. Water at this stage isn’t meant to be a major source of hydration. Breast milk or formula still provides most of the fluid your baby needs, and water is more about getting them used to the taste and the skill of drinking.
A few sips at each meal is a practical way to stay within that range without overthinking it. You don’t need to measure precisely. Just avoid offering a full bottle of water or letting your baby drink freely from a large cup, since it’s easy to overshoot those small daily amounts.
What Type of Cup to Use
An open cup is the best first choice, followed by a straw cup. Both encourage healthy mouth and tongue development. Hard-spout sippy cups, while popular, can interfere with the development of oral muscles and speech patterns over time.
When using an open cup with a 6-month-old, hold it for them and tip it just enough for a tiny amount of water to reach their lips. A helpful rhythm: count “one, two” in your head, then take the cup away. That brief pause between sips prevents your baby from getting too much water too quickly. Expect some spilling and sputtering at first. Offer the cup at mealtimes so your baby starts to associate drinking water with eating solid food.
After the First Birthday
Once your child turns 1, water becomes a more regular part of their diet. Most toddlers transition away from formula entirely around 12 months, and breastfeeding frequency often decreases. Water and whole milk become the primary drinks. There’s no strict upper limit the way there is for younger infants, but offering water throughout the day with meals and snacks is enough to keep a toddler well hydrated. Juice, flavored waters, and sweetened drinks aren’t necessary and can crowd out more nutritious options.
When Tap Water Needs Extra Attention
For most healthy babies over 6 months in areas with treated municipal water, regular tap water is fine. If your baby is younger than 2 months, was born prematurely, or has a weakened immune system, boiling water before use adds an extra layer of safety. Bring it to a full boil, then let it cool completely to room temperature before offering it.
During emergencies like floods, hurricanes, or water main breaks, tap water may not be safe. In those situations, use bottled water or boil tap water regardless of your baby’s age. If you’re unsure about your local water quality, your pediatrician or local health department can point you to testing resources. Well water, in particular, can contain contaminants that aren’t regulated the same way municipal supplies are, so testing is worth doing before your baby starts drinking it.