A 10-month-old can have 4 to 8 ounces of water per day, which works out to about half a cup to one cup. This is a small, supplemental amount. Breastmilk or formula still provides the vast majority of your baby’s hydration and nutrition at this age.
The Daily Water Range
Both the CDC and the American Academy of Pediatrics recommend 4 to 8 ounces of water per day for babies between 6 and 12 months old. At 10 months, your baby is eating more solid foods than they were a few months ago, which creates a modest need for extra fluid. But that need is small. UC Davis Health suggests offering about 2 to 4 ounces twice a day as a practical way to split it up, such as a little water with each meal.
You don’t need to hit a precise target. The purpose of water at this age is partly practical (helping wash down solid food) and partly developmental (learning to drink from a cup). A few sips at mealtimes is enough for many babies, and it’s unlikely to replace much breastmilk or formula intake.
Why Breastmilk and Formula Still Come First
At 10 months, your baby should still be getting three to four breastfeeding sessions per day or three to four bottles of formula at roughly 6 to 7 ounces each. These feedings deliver calories, fat, protein, and hydration all at once. Water has none of those things. If a baby fills up on water, they may drink less milk, which means fewer calories and nutrients during a critical growth period.
Think of water as a companion to meals, not a replacement for milk. Offering it in small amounts alongside solid foods keeps the balance right.
The Risk of Too Much Water
Giving a baby too much water can cause a dangerous drop in sodium levels, a condition called water intoxication. It happens when excess water dilutes the sodium in the blood, causing cells (especially brain cells) to swell. Symptoms include unusual irritability or sleepiness, low body temperature, puffiness, and in severe cases, seizures.
Babies under 6 months are at the highest risk because their kidneys are still immature and they have a strong hunger drive that can lead them to drink large volumes of any liquid offered. By 10 months, kidney function is more developed, but the risk doesn’t disappear entirely. Sticking to the 4-to-8-ounce daily range keeps you well within safe territory. Avoid watering down formula, which is another common way babies accidentally take in too much water relative to nutrients.
Best Ways to Offer Water
At 10 months, water is also a tool for building drinking skills your baby will need by their first birthday. The goal is for babies to be comfortable drinking from an open cup around age one, so now is a good time to practice. Put just a few sips of water in a small open cup and help your baby hold it. Spills are completely normal.
A straw cup is another strong option. The sucking motion required for a straw is different from breast or bottle feeding, so it helps your baby develop a new skill. Traditional spouted sippy cups, on the other hand, use the same sucking motion as a bottle and don’t build those more advanced drinking abilities. If you do use a sippy cup as a transition tool, a spoutless design is a better choice, and aim to move to an open cup by the first birthday.
Offering water during meals and snack times, rather than between feedings, helps ensure it complements solid food without interfering with milk intake.
Fluoridated Water Considerations
UC Davis Health specifically recommends offering fluoridated water when giving water to babies in this age range. Fluoride supports developing teeth. You can check with your local water utility to find out whether your tap water is fluoridated. If it is, tap water does double duty as both hydration practice and early dental care.
Signs Your Baby Is Well Hydrated
You probably won’t need to count ounces precisely if you know what good hydration looks like. A well-hydrated 10-month-old produces at least six wet diapers per day, has a moist mouth, tears when crying, and a soft spot on the head that looks normal (not sunken).
Early signs of dehydration include fewer wet diapers, a dry or sticky mouth, fewer tears, less playfulness than usual, and a sunken soft spot. More severe dehydration shows up as extreme fussiness or excessive sleepiness, sunken eyes, cool or discolored hands and feet, wrinkled-looking skin, and only one to two wet diapers in a full day. Dehydration in babies most commonly happens during illness, especially with vomiting or diarrhea. During those times, increasing breastmilk or formula feeds is more effective than pushing plain water.
Quick Reference by Fluid Type
- Breastmilk: About 4 nursing sessions per day, on demand
- Formula: 6 to 7 ounces per feeding, 3 to 4 times per day
- Water: 4 to 8 ounces total per day, offered in small amounts at meals
- Juice, cow’s milk, and other drinks: Not recommended before 12 months