A 10-month-old can have 4 to 8 ounces of plain water per day. That’s roughly half a cup to one cup total, spread across the day rather than given all at once. Both the CDC and the American Academy of Pediatrics set this range for all babies between 6 and 12 months who are eating solid foods.
Why the Limit Is So Low
At 10 months, breast milk or formula is still your baby’s primary source of both nutrition and hydration. Water doesn’t contain the calories, fat, or nutrients a baby needs for growth, and too much of it can fill up a small stomach, leaving less room for the milk feeds that matter most. The goal of offering water at this age isn’t really hydration. It’s to help your baby get familiar with the taste of plain water and practice drinking from a cup.
Water Intoxication: The Real Risk
Infant kidneys are immature and can’t flush large volumes of water efficiently. When a baby takes in too much water relative to their body size, sodium levels in the blood drop rapidly, a condition called hyponatremia. According to the CDC, symptoms of water intoxication in infants include irritability or unusual sleepiness, low body temperature, swelling, and seizures. These symptoms can appear when total body water increases by as little as 7% to 8%. For a baby weighing around 20 pounds, that threshold is reached faster than most parents would expect.
Sticking to the 4-to-8-ounce daily range keeps you well within safe territory.
When and How to Offer Water
The best time to offer water is during meals. A few sips alongside solid food helps your baby learn to wash food down and gets them used to drinking something other than milk. You don’t need to offer water between meals or push your baby to finish a set amount. If they take a sip or two at lunch and a sip or two at dinner, that’s plenty.
For cup type, an open cup is ideal for building oral motor skills. Small, two-handled training cups work well because they’re easy for little hands to grip. Sippy cups and straw cups are fine too, especially when you need to limit spills. Practicing with an open cup, even in small doses, strengthens the muscles in your baby’s mouth, tongue, and jaw, which supports both eating and speech development later on.
What Counts Toward the Daily Total
The 4-to-8-ounce guideline refers to plain drinking water only. It doesn’t include the water content in breast milk, formula, or foods like purees and fruits, all of which contribute to your baby’s overall hydration. If your baby is still breastfeeding or taking formula regularly throughout the day, they’re already getting the vast majority of the fluid they need.
Small amounts of water used to thin purees or mixed into baby cereal generally don’t need to be counted toward the daily limit, since the volumes are tiny and absorbed along with food.
Other Drinks at 10 Months
Breast milk and formula should remain the main beverages until your baby turns one. The AAP recommends avoiding juice for as long as possible, though if it’s introduced between 6 and 9 months, it should be capped at 4 to 6 ounces per day. Flavored milks, squashes, juice drinks, and anything fizzy are best avoided entirely at this age. They can fill your baby up without providing meaningful nutrition, and the sugar can affect developing teeth. Water and milk are the only drinks a 10-month-old needs.
Signs Your Baby Is Well Hydrated
You don’t need to measure water intake down to the ounce. Instead, watch for the basics: your baby should be producing several wet diapers throughout the day, and their urine should be pale. Signs that something is off include a sunken soft spot on top of the head, sunken eyes, few or no tears when crying, noticeably fewer wet diapers than usual, and unusual drowsiness or irritability. In hot weather, you can offer slightly more water, but the same general range applies. If your baby seems thirsty on a warm day, an extra ounce or two is reasonable.