After drinking so much water during pregnancy (the thirst is real), you might be surprised to learn that your new baby shouldn’t be drinking plain water at all. In fact, babies get all the hydration they need through breast milk or nutrient-rich formula.

Read on to find out why young babies should not drink water, when to start giving water and the symptoms of dehydration in babies.

When can babies start drinking water?

In general, your baby does not need to drink water until he is 6 months old. Until then, they get all the hydration they need from breast milk or formula, even in hot weather. Once your baby is about 6 months old, it’s okay to give her sips of water when she’s thirsty.

You may have heard of colic water, a popular herbal remedy for colic and other gastrointestinal problems in babies. Although there is no medical evidence to suggest that stagnant water works, many parents swear by it. If you’re thinking about trying it, talk to your pediatrician first.

Why can’t babies drink water?

Your baby’s kidneys, the key organs for filtering blood and processing water in the body, are not yet fully mature. Drinking plain water could disrupt their electrolyte balance, leading to serious health consequences such as seizures.

Additionally, drinking plain water can fill their bellies, making them too full to get enough breast milk or formula. Never give your baby water as a substitute for breast milk or formula, which are full of nutrients your baby needs.

We started giving a (very small) open cup of water with meals at 6 months. Most of it took a long time to spill, but I didn’t want to practice with an open cup of my precious expressed breast milk!

– Member of the BabyCenter merrygoose community

How much water should a baby drink?

Once your baby starts solids around 6 months of age, it’s also okay to start offering sips of water from an open cup or straw as practice, but I still wouldn’t exceed 8 ounces in a day.

“We started giving a (very small) open cup of water with meals at 6 months,” he says BabyCenter Community member of merrygoose. “Most of it took a long time to spill, but I didn’t want to practice with an open cup of my precious expressed breast milk!”

Focus on giving fluids in the form of breast milk or formula. Your baby will naturally get water from eating fruits and vegetables. You don’t have to worry about drinking a certain amount of water every day.

After your baby’s first birthday, you can give her a cup of water to drink with meals and whenever she’s thirsty.

Experts recommend giving toddlers at least 32 ounces of fluid a day, but they need a maximum of 16 to 20 ounces of cow’s milk (more can contribute to anemia or constipation). The rest can come from plain water and the fruits and vegetables you give them, as well as breast milk if your child is still breastfeeding.

Can babies have tap water?

In general, the best water to give your baby is tap water. The US Environmental Protection Agency regulates tap water quality and sets legal limits for more than 90 contaminants. Although water contamination does occur, the water that comes out of your faucet is usually the safest option.

“(Using tap water or bottled water) depends on where you live,” he says BabyCenter Community member Stephibxo. “My pediatrician told me that because of where I lived, tap water in my specific area would be beneficial for installation, but I could also use filtered/bottled water.”

If you are concerned about the quality of your tap water, you can test it and use a suitable water filter if necessary. Contaminants to watch out for include microorganisms and bacteria (like E. coli and Giardia), organic chemicals from agricultural pesticides (like glyphosate), nitrates and nitrites from agricultural fertilizers, disinfection byproducts like chloroform, and industrial chemicals like benzene. The material your water pipes are made from can also contaminate your tap water – it’s especially important to make sure your water is lead-free if you have lead or brass pipes.

In parts of the United States, tap water is treated with fluoride, which helps prevent tooth decay. But if your baby consumes a lot of fluoride before her teeth erupt, she may develop fluorosis, which looks like pale white lines or streaks on the teeth. You cannot develop fluorosis after the teeth break through the gums.

Fluorosis does not affect the health of the teeth, and it is possible that only a dentist would notice it. To prevent this, talk to your child’s doctor to determine if your baby may be getting too much fluoride.

To learn more about the quality of your tap water, you can check the annual for your area Consumer Confidence Report. To test your home’s tap water, your local water agency or health service can do this, or you can have it tested by a laboratory with a state certificate.

Bottled water is fine too—it’s regulated by the Food and Drug Administration—but since tap water is usually safe for your baby, it’s not necessary to give her bottled water.

Learn more about the safety of tap and bottled water, and whether babies can have sparkling water.

What you need to know about water poisoning in babies

In very rare cases, a baby who drinks too much water can develop water intoxication, which can cause seizures, coma and brain damage. Water poisoning occurs when too much water dilutes the body’s sodium concentration, disrupting the body’s electrolyte balance and causing swelling of internal tissues and organs.

Liz Donner MD, a pediatric hospitalist and BabyCenter advisory board member, notes that symptoms can include confusion, blurred vision, vomiting, altered breathing, fatigue and difficulty concentrating.

Is it ok to dilute the formula with water?

Do not try to stretch the formula by diluting it with water – follow the directions on the package carefully for making the formula and use the recommended amount of water. If you add too much water to your baby’s formula, your baby could develop a serious electrolyte imbalance and may not get all the nutrients he needs.

What to do if your baby is dehydrated

If your baby doesn’t drink enough fluids or loses more of the fluids he takes in (because he’s sick and vomits or has diarrhea, for example), he may become dehydrated. Symptoms that your baby is dehydrated include:

• They play less than usual
• Wets less often (for babies, this may mean fewer than four wet diapers a day)
• Their mouths are dry or sticky
• If your baby still has a soft spot on his head, he may become sunken

If your baby shows signs of dehydration, call your doctor. They may want to see your baby to check them. If your baby is under 3 months old, they will probably recommend that you give your baby more breast milk or formula than usual. If your baby is older than 3 months, he may recommend giving him some water or an electrolyte drink like Pedialyte.