When can newborns have water? From what age, how much and what about tea

It's 34 °C (93 °F), your baby is three months old with a sweaty neck, and someone in the family says, with all the care in the world: “Give the poor thing some water, they must be thirsty.” It isn't just grandma: in a study from India on breastfed babies in summer, 97% of the nurses and 63% of the doctors asked before the measurements were taken recommended water. The advice comes from an intuition that is right for adults.

When can newborns have water? The short answer:

• Under 6 months, breastfed: no, not even in a heat wave. If they seem thirsty, you put them to the breast instead of giving water. On this point, all the infant feeding guidelines we read say the same thing.
• Under 6 months, formula-fed: normally, no. In a heat wave, the guidelines disagree: the UK allows a few sips of cooled boiled water; the US and Germany say more frequent formula feeds, not water; in Australia, the website for parents says the same, while the guideline for doctors allows cooled boiled water if extra fluids are needed. Never replace a feed with water, and never dilute formula.
• From 6 months: sips from a cup (in Germany, practice sips from the first puree; water becomes necessary once they're eating three puree meals a day, usually around 7–9 months). The US consensus guideline gives 120–240 ml (4–8 oz) a day up to their first birthday and acknowledges that, in practice, a baby won't swallow much of the water offered.
• Between 1 and 2 years: water becomes the everyday drink, alongside milk; according to the same guideline, 240–950 ml (8–32 oz) a day, depending on how much milk they still drink.

Under 6 months, the exact month doesn't matter: at one month, at 2, 3, 4 or 5 months, the answer is the same.

What the guidelines say: they agree on breastfed babies, not on formula in a heat wave

The table puts the recommendations of the World Health Organization (WHO) side by side with the official ones from five countries.

For formula-fed babies in hot weather, we didn't find any study comparing the two pieces of advice (we searched PubMed). The guidelines that allow water don't say why; the physiological argument is that formula gives the kidneys more salts to get rid of than breast milk does. The ones that don't allow it say that correctly prepared formula is enough, “even in summer temperatures,” as the German guideline puts it. In practice: ask your pediatrician; the rules below stay the same.

Can newborns drink water? Not before 6 months, because milk is already water

Breast milk is about 87–88% water: 87.5 grams per 100 grams, according to the food composition tables of the US Department of Agriculture. Ready-to-feed liquid formula has 86–88 grams of water in the same tables, practically the same; powdered formula only gets there if it's mixed exactly as the label says. At every feed your baby is already drinking water; it just comes packaged with calories, protein, fat and salts.

This has been checked in hot weather, too: in Jamaica (27.6 °C, about 82 °F, and 76% humidity), in the Sinai desert, in Peru, in India in the hottest season (35–40 °C, or 95–104 °F, dry air), in Pakistan (up to 40.7 °C, about 105 °F, eight days without water) and in Honduras, the urine of exclusively breastfed babies stayed within normal limits, far from how concentrated their kidneys can make it, so they weren't short of water. A 2022 systematic review included 18 studies, nine of them of this kind, and found no evidence that babies under 6 months need extra fluids in hot weather.

The studies have limits: they're small, most of them are old, they mainly measured urine, and they were done in healthy, breastfed babies. They say nothing about formula-fed babies.

The only heat experiment with a comparison group that we found, from India, published in 1991, followed 45 boys aged 1–4 months in rooms at 34–41 °C (93–106 °F). Those whose mothers gave them water, as they usually did, took less milk during the eight hours of observation, 210 ml versus 274 ml, and were no better hydrated: urine, blood, weight and temperature came out the same.

Two newer studies, at 4 and at 5 months, did not find that water or tea reduced the amount of milk taken per day. What still holds, across all the studies, is that under 6 months water brings nothing that milk doesn't already provide. And in developing countries, breastfed babies under 6 months who were also given water or tea had about a quarter more episodes of diarrhea and ended up in the hospital because of it more than twice as often.

Water intoxication in infants: rare, serious and with a specific pattern

Water without salts, drunk in large amounts, dilutes the sodium in the blood; this is called hyponatremia. When sodium drops quickly, water moves into the cells, and brain cells swell. That's where the seizures come from.

A children's hospital in St. Louis treated 34 cases in 15 years: 31 were babies from poor families, and the most common reason was that the formula had run out and they'd been given water instead. A hospital in Wisconsin, after two new cases, went through ten years of records and found another 27 babies under one year old admitted with seizures from low sodium, all after too much water without salts. A case from 2024: a five-month-old girl fed formula every one to two hours, plus 100 ml (about 3.4 oz) of water every three hours, between feeds.

The pattern: a lot of water, in a small baby, either instead of milk, mixed into the formula, or given on top, bottle after bottle (less often juice, soda or tea), often when the formula had run out or the child was sick. Almost all the cases we read that say how the child was fed involve formula-fed babies; the fault isn't with formula made up as the label says, but with the water given instead of it, in it or on top of it. We found only one published case in a breastfed baby: a two-day-old boy in a maternity ward in Norway, on a hot day. He was sweating, and his mother gave him water in addition to the breast, which he drank eagerly: about 350 ml (12 oz) in a few hours. He had seizures and recovered completely.

How often does it happen? We didn't find any population-level figure, only counts from a few hospitals, mostly American, from the 1980s and 1990s: some authors at the time called it common in the US; a 2007 European review called it rare, occurring in exceptional circumstances. The children in the case reports we read in full recovered completely, even those who needed a ventilator, but the authors of the 2024 case note that, in published cases, outcomes ranged from full recovery to lifelong after-effects.

How much is “too much water”? We didn't find any study that gives a threshold, so any figure in milliliters or ounces you see online is a guess. The cases show amounts on the scale of bottles, not teaspoons: 350 ml in a few hours in a newborn, three bottles of water a day for several days, 100 ml every three hours, almost 150 ml per kilogram of body weight in a single day.

The signs, as they appear in the case series:

• unusually sleepy or hard to wake, or, on the contrary, irritable;
• cold: a temperature below 36.5 °C (97.7 °F), even in a heat wave. It seems like a paradox, but it's a useful sign: in one American hospital, among babies under 6 months who came to the ER with seizures and no other obvious cause, a low temperature was the best clue to hyponatremia. It doesn't show up in every baby: the five-month-old girl had a normal temperature;
• puffy eyelids or face;
• seizures (in a small baby they may look like nothing more than twitching of the eyes or of one arm) or pauses in breathing.

If they've been given water and you see any of the signs above except irritability, call 911; if they're only irritable, call your pediatrician the same day. And one sign that does not reassure: lots of wet diapers; the five-month-old girl was peeing a lot and was being changed every two to three hours.

The explanation you hear everywhere, “a baby's kidneys are immature,” is only partly true: the kidneys filter slowly in the first days and weeks, which is why a newborn is the most vulnerable, but a healthy baby can make very dilute urine; in the published cases, what mattered was the combination: a lot of water without salt, a small body, water drunk quickly or instead of milk, sometimes an illness too. Nor is it only a question of age: in a British series from 1999, four children between 9 months and almost 3 years had seizures after liters of diluted juice or watered-down milk: three of them daily, for weeks or months on end, the fourth in a single day. After 6 months, the risk doesn't come from a cup of water with a meal, but from very large amounts of diluted drinks that take the place of food and milk.

Grandma already gave them water: is it serious, and what do you do now?

If it was a few teaspoons or sips, once, the situation is nothing like any of the cases above, where whole bottles were drunk. You don't need to do anything special: the next feed comes as usual; don't delay it and don't “make up” for it. Just don't keep going.

If the water or tea took the place of a feed, if it was given bottle after bottle, or if a baby only a few days or weeks old drank a whole bottle, call your pediatrician the same day, even if they seem fine. And if they're unusually sleepy or hard to wake, cold, puffy in the face, have a seizure or have pauses in their breathing, call 911.

And so you have something to tell grandma without an argument: in Lesotho, grandmothers considered giving water to babies a new habit, brought in from the clinic, and avoided it as unnecessary. What looks like “how it's always been done” was, there as in the study from India, the medical advice of the time, not grandma's mistake.

In a heat wave: what to do instead of water, and what changes after 6 months

If you're breastfeeding: put them to the breast whenever they ask. In hot weather, says the British guideline, they may want to feed more often (we didn't find a measurement of how much more often). Many guidelines explain this with the milk at the start of a feed, “more watery,” which supposedly quenches thirst; what has been measured is that the fat in the milk rises over the course of a feed, and we didn't find a study showing that babies choose short feeds on their own in order to drink. For what you do, it makes no difference: breastfeeding on demand covers both thirst and hunger.

If you're formula feeding: make it up exactly as the label says and offer the bottle more often if they seem to want it, without adding water to “thin it out”: diluted formula is one of the causes in the cases above. If your country's guideline allows a few sips of cooled boiled water and your doctor agrees, they go between feeds, not in place of them.

For both: under 6 months, no direct sun at all; for older babies, shade matters most at peak hours (11:00–15:00 in the UK, 10:00–16:00 in the US, 11:00–18:00 in the heat wave recommendations published by Romania's public health departments). Light clothing; at night, in a heat wave, just a diaper or a thin bodysuit, and no blanket over the stroller; during the day, curtains drawn, and for sleep, as cool as you can manage (16–20 °C, or 61–68 °F, according to British guidelines; the rest is in the guide for when your baby won't sleep).

Over 6 months, in a heat wave you can offer water from a cup between meals too, not just with them, as the British guideline says.

If in a heat wave they ask to feed more often and sleep more restlessly, the useful question isn't “are they thirsty?” but “do they have enough wet diapers?”

Signs of dehydration in infants, and why it isn't treated with water

If you see one or more of the signs below, taken from the British and American guidelines for parents, call your pediatrician the same day:

• fewer wet diapers than usual. As a benchmark, from the British page on breastfeeding: from day five, a breastfed baby who is feeding well has at least six wet, heavy diapers in 24 hours; in the first 48 hours, only two or three in total. The American Academy of Pediatrics says to call the doctor within 24 hours if, after the first five days, there are fewer than six a day. The British page on dehydration doesn't give a number, but compares with what your child usually does (more day-by-day benchmarks in the guide to how much newborns sleep);
• dark, strong-smelling urine;
• dry mouth, crying without tears;
• a sunken fontanelle (the soft spot on top of the head) or sunken eyes;
• unusually sleepy or irritable.

Take them to the doctor or the ER right then, not the next day, if, after the first days of life, they haven't had a wet diaper in more than eight hours, or if their mouth is very dry and they cry without tears. Call 911 or go to the ER if they haven't peed in 12 hours, are hard to wake, have skin that feels cold to the touch or looks pale or mottled, have blue or gray lips or tongue, are breathing very fast or with difficulty, have a seizure or, under three months, have a fever of 38 °C (100.4 °F) or higher.

Dehydration isn't treated with water. For a breastfed baby, the answer is breastfeeding more often and, the same day, the doctor, who checks whether they're getting enough milk: in one region of northern England, severe dehydration with high sodium in breastfed newborns (at least 2.5 per 10,000 births) had a single cause, breastfeeding that wasn't working. With diarrhea or vomiting, milk continues, in smaller, more frequent feeds; extra fluid, if needed, is an oral rehydration solution from the pharmacy, on your doctor's advice. Plain water and tea aren't the treatment (for a formula-fed baby, the British guideline allows only sips of water between feeds, boiled and cooled if the baby is under 6 months), and you don't dilute formula: the Romanian Ministry of Health's guideline on acute gastroenteritis in children says that water or tea, in large amounts, can cause hyponatremia or hypoglycemia. The British guideline for doctors puts babies under one year, especially under six months, in the group at higher risk of dehydration: one more reason to call early.

How much water should a 6-month-old drink? At first, it's cup practice

When. With the first solid foods, at around 6 months, according to most guidelines (WHO, US, UK, Brazil, Spain). In Germany and Hungary water only becomes necessary once the child is eating three solid meals a day (in Germany, usually around 7–9 months), but the German guideline allows a few sips from a cup, as practice, from the first puree. Both approaches are fine; neither is a measured physiological threshold.

How. From a cup or a small glass: the British guideline prefers an open cup or a free-flow cup without a valve, while the American one also accepts a sippy cup or a straw cup. The German guideline says to offer it at meals and between them, but not in the half hour before a meal; the Brazilian one, mostly between meals. No sugar and no honey in the water (honey, not at all under one year).

How much. The old article on this page gave “30–60 ml a day at first”; we didn't find that figure in any official guideline, only on a few Romanian websites, with no source. What does exist:

• US (the 2019 consensus guideline, also signed by the American Academy of Pediatrics): 120–240 ml (4–8 oz) a day between 6 and 12 months and 240–950 ml (8–32 oz) a day between 1 and 2 years. The same guideline says water shouldn't replace milk. On another page, also from the American Academy of Pediatrics, the cap is more cautious: no more than 120 ml (4 oz) a day, up to 240 ml (8 oz) on very hot days;
• Germany: about a glass (200 ml, or 7 oz) a day, once the child is eating three puree meals, and 600–700 ml (20–24 oz) a day after they move on to family food;
• UK: no figure, just “sips of water with meals.”

If you see “800–1,000 ml a day at 6–12 months” somewhere, the figure is real, but it's all the water, from milk, from food and from everything they drink, not the water to give in a cup. Until their first birthday, the main drink is still milk.

What water. Tap water, if it's fit to drink, is fine: according to the British guideline it no longer needs boiling after 6 months; according to the German one, as a rule it doesn't need boiling; and the Australian one calls for boiling until one year. Formula, however, is made with boiled water that's still at least 70 °C, or 158 °F (cooled for no more than half an hour), at any age, according to the WHO and the British guideline. Bottled water should be low in sodium (in Germany, water for infants by law has at most 20 mg of sodium and 10 mg of nitrates per liter). Well water needs a nitrate test: babies fed formula made with it are a high-risk group, says the American Academy of Pediatrics. Boiling doesn't remove nitrates, it concentrates them; if there are too many, the Minnesota Department of Health calls for water from another source, bottled for example, and no well water at all for babies under 6 months, not even in formula.

What the day looks like, from waking up and the first feed to bedtime, month by month:

Newborn · 1 month · 2 months · 3 months · 4 months · 5 months · 6 months · 7 months · 8 months · 9 months · 10 months · 11 months · 12 months

At what age can babies have tea: chamomile, fennel and other remedies

In short: under 6 months, no, for the same reasons as water (for the WHO and UNICEF, a baby who gets tea is no longer exclusively breastfed). After 6 months, it depends on the country: the Brazilian guideline allows chamomile, lemon balm or mint tea, unsweetened and without replacing a meal; the German one, once solids start, allows unsweetened teas suitable for infants, but not as the only drink; the British and Australian ones don't recommend herbal teas for infants. Fennel tea isn't recommended under 4 years, and teas also have problems of their own:

• Fennel. The European Medicines Agency doesn't recommend it under 4 years because of a lack of safety data. The substance of concern is estragole, from the seeds: the agency asks that young children's exposure to it be kept as low as possible, and calculations on commercial teas gave, for babies, results ranging from well below to about 20 times above its reference level for children. Among the reactions reported to the authorities there is also an eight-week-old premature baby with seizures from low sodium after fennel tea; the cause isn't proven, but the mechanism would be the same as with water.
• Chamomile. The same agency gives doses of chamomile tea only from 6 months; under 6 months its use “is not established,” explicitly for reasons of nutrition and fluid intake. In a study from Argentina, 7.5% of 200 chamomile samples contained botulism spores, more often in loose chamomile than in tea bags, and the German guideline warns that chamomile, mint and lemon balm teas can contain high levels of pyrrolizidine alkaloids, which is why it doesn't want them as the only drink.
• Sugar. Instant teas and many “baby” teas contain sugar or glucose; sipped often or continuously, they can cause severe tooth decay even before the teeth come in, warns the German Federal Institute for Public Health.
• Colic. A 2016 Cochrane review couldn't recommend herbal remedies, based on small studies with a high risk of bias; what does have evidence is in the colic guide.
• Gripe water. Is it OK for newborns? We didn't find any randomized study. The licensed British version contains sodium bicarbonate and isn't meant for babies under one month.
• Sugar water or glucose water for jaundice. The WHO doesn't recommend it, because it can make the baby nurse less; the 2014 Italian neonatology guideline doesn't want it routinely for breastfed babies either.
• Constipation. In a breastfed baby it's very rare, and long gaps between stools can be normal; for a formula-fed baby, the British guideline allows cooled boiled water between feeds. Talk to your doctor first.
• Juice isn't recommended under one year in the US, Brazil and Poland; the British guideline says it isn't needed, and if you give it anyway, diluted 1 part to 10 parts water and only with meals.

In the US, bottled water sold “for babies” doesn't change the under-6-months rule: in the Wisconsin case series, two babies had seizures after being given a bottled water marketed specifically for infants. And for preparing formula, the American Academy of Pediatrics calls for boiled water only for babies who are under 2 months old, were born prematurely or have a weakened immune system; otherwise, tap water is fine, as long as the local supply has no known contamination. The American rule is less strict than the British guideline and the WHO, which call for water of at least 70 °C (158 °F) at any age.

How Lulla helps

In Lulla, the Feeding log (breastfeeding on one side or both, with a timer; bottle in milliliters; solid food; water) and the Diapers log (wet, dirty or both) are free. If you pick water for a baby under 6 months, the app explains the first time why it isn't needed, and it doesn't show any reference amount or total under the field. The Diapers card on the Home screen shows today's numbers, and the list keeps 30 days, so you can compare with your usual days yourself: the app doesn't give you dehydration alerts or diaper thresholds, but it gives you the numbers to have in hand when you call the doctor. With Premium, Stats shows feeds and diapers day by day, over 7 or 30 days, plus fluids, if you log milliliters.

Keep in mind: this article is for information, not medical advice, and its recommendations come from the guidelines and studies in the source list, each with its own limits. For any concern about your child's hydration, feeding or growth, your pediatrician is still the first place to go: they know your child's history.