When Can Babies Drink Water?

Water by age

How much plain water is appropriate at each age. Breast milk or formula stays the main drink until 12 months.

Age	Plain water	Main drink	Cup to use
0-6 months	None (unless your pediatrician says otherwise)	Breast milk or formula	Bottle / breast
6-12 months	Small sips, up to about 4-8 oz (0.5-1 cup) a day	Breast milk or formula	Open or straw cup
12-24 months	About 8-32 oz (1-4 cups) a day	Whole milk (about 16 oz / 2 cups) + water	Open or straw cup

Why no water before 6 months

Until around 6 months, breast milk and formula supply all the water a baby needs, even in hot weather. A young baby's stomach is small, so water takes up room that should go to the calories and nutrients in milk. Filling up on water can mean a baby eats less and gains weight more slowly.

The bigger reason is safety. A baby's kidneys are still developing and cannot clear extra water well. Too much water dilutes the sodium in the blood, which can cause a condition called water intoxication.

What water intoxication is

Water intoxication happens when too much plain water lowers the level of sodium in the blood. That state is called hyponatremia. Sodium helps control the fluid balance inside and around cells, so when it drops too low, cells take on water and swell, including cells in the brain.

In babies this can lead to low body temperature, puffiness or swelling, unusual drowsiness, irritability, and in serious cases seizures. It can come from giving plain water before 6 months, from watering down formula to stretch it, or from offering large amounts of water at once. This is why the amount matters, not just the age, and why sips rather than full bottles are the rule once water is introduced.

How to start water at 6 months

Once your baby is eating solids, water is mostly about practice with a cup, not about replacing milk.

• Offer water in an open cup or a straw cup, not a bottle, so it stays a small amount and builds a useful skill.
• A few sips with meals is plenty. Aim for no more than about 4-8 oz across the whole day between 6 and 12 months.
• Keep breast milk or formula as the main drink. Water at this age should not noticeably reduce how much milk your baby takes.
• Plain water only. Babies under 12 months should not have juice or any sweetened drink.
• If your tap water is fluoridated, those small sips also help protect the teeth coming in.

After 12 months

After the first birthday, water becomes a normal everyday drink and your toddler can have it freely, roughly 8-32 oz (1-4 cups) a day depending on size, weather, and activity. This is also when whole cow's milk can become a drink, about 16 oz (2 cups) a day.

Water and milk should be the two main drinks. Juice is still not needed, and if you do serve it, keep it to about 4 oz a day for toddlers and offer whole fruit instead when you can.

Reflects AAP HealthyChildren drink recommendations and CDC infant-toddler nutrition guidance, 2024-2026.

Related questions

Can I give my newborn water in hot weather?

No. Even in heat, a baby under 6 months gets all the fluid they need from breast milk or formula. If you are worried about dehydration, offer more milk feeds and call your pediatrician rather than giving water.

Is it safe to water down formula to make it last longer?

No. Diluting formula lowers the calories and nutrients your baby needs and adds extra water, which can cause water intoxication and dangerously low sodium. Always mix formula exactly as the label directs, and call your pediatrician if cost is a concern.

How much water should a 6 to 12 month old drink?

Only small sips, up to about 4-8 oz (half to one cup) across the whole day, mostly to practice using a cup with meals. Breast milk or formula should still be the main source of fluid at this age.

When can my baby drink cow's milk instead of water?

Cow's milk is not a substitute for water. Plain whole cow's milk can become a drink after 12 months, about 16 oz (2 cups) a day, while water can be offered freely at the same age. Before 12 months, cow's milk should not be used as a drink.

Sources & further reading

1. AAP HealthyChildren — Recommended Drinks for Children Age 5 & Younger
2. AAP HealthyChildren — How to Safely Prepare Formula With Water
3. CDC Infant and Toddler Nutrition — Foods and Drinks to Avoid or Limit

This article reflects current AAP, CDC, FDA, and other public-health guidance and is for educational purposes only. It does not constitute medical advice. ParentFlow is a wellness companion — not a substitute for your pediatrician. For any medical concern, contact your healthcare provider.