When Can Babies Drink Water? A Clear Guide by Age

It seems like the most natural thing in the world to offer a baby a sip of water, especially on a hot day. But for young babies, water is not the harmless drink it is for us — in fact, before 6 months it can be genuinely dangerous. Here is a clear, age-by-age guide to when babies can drink water, how much, and how to keep your baby safely hydrated.

The short answer

Babies do not need — and should not have — plain water until around 6 months. Before then, breast milk or formula provides all the hydration your baby needs, even in hot weather. From around 6 months, once solids begin, you can offer small amounts of water. At 12 months, water becomes a free-flowing everyday drink.

Why water is dangerous for young babies

This surprises many parents, so it is worth understanding. Giving water to a baby under 6 months can cause real harm for two reasons:

• Water intoxication. A baby's kidneys are immature and cannot process extra water well. Too much water dilutes the sodium in their blood, which can cause a dangerous condition called hyponatremia — leading to irritability, drowsiness, low body temperature, and in severe cases seizures. It is rare but serious.
• Displacing nutrition. A baby's stomach is tiny. Water fills them up without any calories or nutrients, so they take less milk — which can affect weight gain and, for breastfeeding parents, milk supply.

Formula must always be mixed exactly to the instructions — never over-diluted with extra water, which carries the same risks. This is why you never add extra water to bottles or offer sips of water to a newborn, even when it is hot.

Staying hydrated in the early months

If your baby seems thirsty or it is hot, the answer is more milk, not water. Breast milk and formula are mostly water and provide everything your baby needs to stay hydrated. Offer extra feeds in hot weather. Signs your baby is well hydrated: regular wet diapers (roughly 6+ a day once feeding is established), and being alert and content.

Watch for signs of dehydration — fewer wet diapers, a dry mouth, no tears when crying, sunken soft spot, or unusual sleepiness — and contact your doctor if you see them, especially during illness. For hydration during sickness in young babies, follow your pediatrician's advice rather than giving water on your own.

From 6 months: introducing water

Once your baby starts solids around 6 months, you can offer small amounts of water — a few sips from an open cup or a sippy/straw cup with meals. Key points:

• Keep it small. Water is for practice and a little hydration alongside solids, not a replacement for milk. Breast milk or formula remains the main drink through the first year.
• Use a cup, not a bottle. Offering water in an open or straw cup helps develop cup-drinking skills and protects emerging teeth.
• Plain water only — no juice, sugary drinks, or flavored water for babies.
• A little is plenty — think a few ounces total across the day at first.

From 12 months: water freely

At one year, your baby can drink water freely whenever they are thirsty, and water (along with whole cow's milk) becomes a main drink as milk feeds reduce. Offer water throughout the day, especially with meals and in hot weather, and keep sugary drinks off the menu.

Drinks to avoid — and what about juice?

As you introduce water, it helps to know what *not* to offer. Fruit juice is not recommended for babies under 12 months — even 100% juice adds sugar with little benefit, can displace milk and solids, and is hard on emerging teeth. After the first birthday, juice is best limited to a small amount if given at all, and always in a cup, not a bottle. Also keep away from sugary drinks, sodas, flavored or sweetened waters, tea, coffee and any caffeinated drinks, none of which belong in a baby's diet. Cow's milk as a main drink should wait until 12 months, since it is not a suitable substitute for breast milk or formula before then (small amounts mixed into food from around 6 months are fine). And skip plant-based "milks" as a main drink in the first year unless your pediatrician specifically advises one for an allergy or dietary reason. The simple rule for the first year: breast milk or formula as the main drink, small sips of plain water with solids from 6 months, and nothing sugary.

Frequently asked questions

Can newborns drink water?

No. Babies under 6 months should not have plain water — it can cause dangerous water intoxication and fill their tiny stomachs so they take less milk. Breast milk or formula provides all the hydration a young baby needs, even in hot weather.

When can babies start drinking water?

Around 6 months, once solids begin, you can offer small amounts of water with meals — a few sips from a cup. Milk remains the main drink through the first year, and water becomes a free everyday drink from 12 months.

How much water can a 6-month-old have?

Just small amounts — a few sips with meals, up to a few ounces total across the day. Water at this stage is for practice and light hydration alongside solids, not a substitute for breast milk or formula.

How do I keep my baby hydrated in hot weather?

For babies under 6 months, offer more breast milk or formula, not water — milk is mostly water and hydrates fully. From 6 months you can add small sips of water. Watch for regular wet diapers as a sign of good hydration.

The takeaway

Babies under 6 months should never have plain water — it risks dangerous water intoxication and crowds out the milk they need — so keep hydration to breast milk or formula, even in the heat. From around 6 months you can offer small sips of water with solids in a cup, while milk stays the main drink, and from 12 months water flows freely. When in doubt about a young baby's hydration, especially during illness, offer more milk and call your pediatrician rather than reaching for water. For the solids that water accompanies, see when to start solids.

*This article is general information, not medical advice. Do not give water to a baby under 6 months without your pediatrician's guidance.*