When can babies drink water?

Need help figuring out the right total daily intake? Use the bottle feeding calculator.

Under 6 months: no water

For babies under 6 months, all hydration should come from breast milk or formula. Both are already 80% water. Giving extra water can cause:

• Water intoxication (hyponatremia). Babies' kidneys are immature. Too much water dilutes sodium in the blood, which can cause seizures, low body temperature, and brain swelling. It is rare, but real.
• Reduced milk intake. Water fills the stomach without calories. Babies may take less milk and not get the nutrition they need.
• Lower weight gain. Especially in the first months when every ounce counts.

There is one tiny exception: a pediatrician may suggest 1/2 to 1 teaspoon of water on rare occasions, usually to help baby take medicine. That is it. Do not give water to manage hot weather, hiccups, or fussiness in the first 6 months.

6 to 12 months: small amounts with meals

Once your baby is eating solids (around 6 months), you can offer water. The goal is not hydration. Breast milk and formula still provide that. The goal is cup practice and getting baby used to the taste.

How much: 4 to 8 oz total per day across meals. Offer a small open cup or straw cup at the highchair. A few sips per meal is plenty. Most babies will drink less than an ounce at a time.

Why this is the moment: introducing a cup early makes the eventual bottle-to-cup transition easier. Babies who learn cup drinking at 6 to 8 months are usually off bottles by 15 months. Babies who do not start until later often resist.

12 to 24 months: real hydration begins

After the first birthday, water becomes a real source of hydration. Toddlers transition off formula (or breastfeed less) and add cow's milk or alternatives. Water fills the gap.

How much (the AAP guideline):

• 12 to 24 months: 8 to 32 oz of water per day, plus 16 to 24 oz of milk.
• 2 to 3 years: 16 to 40 oz of water per day, plus 16 oz of milk max.
• 4 to 8 years: 40 to 56 oz of water per day, plus 16 oz of milk max.

These are ranges. A more active toddler in summer drinks more. A toddler eating water-rich fruits and veggies drinks less. Watch the diapers (steady pee output, light yellow, not dark).

What about juice?

The AAP says no juice before 12 months. Even 100% fruit juice. After 12 months, up to 4 oz per day diluted with water. Honestly: skip it. There is no nutritional reason to give juice. Whole fruit gives the same nutrients with fiber. Juice trains a sweet preference and can contribute to early tooth decay.

What kind of water?

• Tap water: generally fine if your area has safe municipal water. Run cold water for 30 seconds before filling. Test your water if you live in an older home (lead pipes) or have a private well.
• Bottled water: fine, but check the fluoride content. Most bottled waters have no fluoride, which is needed for tooth development.
• Fluoride: after 6 months, babies need some fluoride. If your tap water has fluoride, that is enough. If you use bottled water only, ask your pediatrician about a fluoride supplement after 6 months.
• Distilled or filtered water: fine for occasional use, but check fluoride status.

What about formula mixed with water? If your tap water is safe, use it cold and bring to a rolling boil if your pediatrician advises (or if water quality is uncertain). Otherwise, bottled water or nursery water (which has fluoride added) is fine.

Best first cups

• Open cup (6 to 8 months): a tiny silicone cup or shot glass-sized cup. Messy, but it teaches actual drinking, not sucking. The skill transfers to any cup later.
• Straw cup (7 to 9 months): a weighted straw cup makes the suck-to-flow transition easier. Many feeding therapists prefer straw cups over hard-spout sippies.
• 360 cup (10 to 12 months): rim-drinking cups that act like an open cup with a leak-proof valve. Great for transition.

What to skip: traditional sippy cups with hard spouts. They can affect oral development and tooth alignment if used heavily for more than a few months.

Signs your baby is dehydrated

For babies (and toddlers), watch for:

• Fewer than 6 wet diapers in 24 hours (for babies under 1) or fewer than 4 wet diapers for toddlers.
• Dark yellow urine.
• Crying without tears.
• Sunken soft spot (fontanelle) on a baby's head.
• Dry mouth and lips.
• Unusual sleepiness or fussiness.
• Cool, mottled hands and feet.

Severe dehydration is a pediatric emergency. Call your pediatrician immediately, or go to the ER if a baby under 6 months has any of these signs.

When the rules flex

A few cases call your pediatrician (not the internet) for guidance:

• Heat wave with a baby under 6 months. The answer is usually more frequent breast or formula feeds, not water. But ask.
• Stomach bug or fever. Your pediatrician may suggest an oral rehydration solution, not plain water.
• Constipation. Once eating solids, an ounce or two of water with each meal can help. Before solids, it is usually a milk issue, not a water issue.
• Premature babies. Use adjusted age and follow your pediatrician's specific guidance.

The takeaway

Under 6 months: just milk. From 6 to 12 months: small amounts to learn the cup, not for hydration. After 12 months: real hydration. The first sip of water is a quiet milestone but a useful one. Take it slow.