Babies under 6 months need only breast milk or infant formula — no water. From around 6 months you can start offering small sips of water from a cup, usually with meals, while milk stays the main drink until 12 months. The details differ a little by country: Australia says no water before 6 months even in hot weather and to boil tap water until 12 months, while the NHS allows sips of cooled boiled water for formula-fed babies in the heat and says water for babies over 6 months doesn't need boiling.
Can babies under 6 months drink water?
No. Pregnancy, Birth and Baby, the Australian Government's parenting service, says water is not recommended for babies younger than 6 months. The WHO recommends exclusive breastfeeding — breast milk only — for the first 6 months, and the NHS says fully breastfed babies don't need any water until they've started solid foods.
There are two reasons:
- It can upset the balance in your baby's blood. Pregnancy, Birth and Baby explains that a young baby's stomach and kidneys are very small, and giving them water can change the concentration of certain nutrients in their blood. It describes this as very dangerous and even fatal. This is sometimes called water intoxication.
- It fills them up. Water has none of the nutrients your baby needs. A baby who drinks water may not drink enough breast milk or formula to grow well.
Breast milk and formula already contain the water your baby needs. If your baby seems thirsty, offer a feed. Always make formula up exactly as the instructions on the tin say — see preparing formula.
Can I give my baby water in hot weather?
This is where guidance differs by country.
| Source | Babies under 6 months in hot weather |
|---|---|
| Pregnancy, Birth and Baby (AU) | Breast milk or formula only; do not offer water. Offer extra or more frequent feeds |
| NHS (UK) | Breastfed babies may feed more. Formula-fed babies may need small sips of cooled boiled water as well as usual milk |
| AAP (US) | Breast milk as the sole source of nutrition for about 6 months; water isn't listed before 6 months |
Whichever applies to you, the first step in the heat is the same: offer feeds more often. Pregnancy, Birth and Baby notes babies may want to feed more often but for shorter periods in hot weather. For breastfeeding in the heat, it suggests putting a towel or pillowcase between you and your baby, lying down to feed to reduce skin contact, and making sure you drink enough water yourself.
For babies over 6 months, you can offer water in hot weather as well as milk. See our hot weather guide for keeping your baby cool.
When can babies start drinking water?
From around 6 months, when your baby starts solids. Pregnancy, Birth and Baby says you can begin offering small amounts of water, but it shouldn't replace breast milk or formula, which remain the main drink until 12 months.
How much? The AAP's drinks guide and the CDC both suggest about 4–8 oz (120–240 mL) a day in total for babies aged 6 to 12 months. That's a small amount — roughly half a cup to a cup across the whole day. The AAP's main reason for offering it is to build cup-drinking skills and get your baby used to the taste of water.
How to offer it:
- Offer a few sips from an open cup, or a free-flow cup without a valve, at mealtimes. The NHS says these help babies learn to sip and are better for teeth.
- Hold the cup for your baby at first and let them take small sips.
- Expect most of it to end up on their chin and bib for a while — that's how cup skills develop.
- Keep milk feeds going as usual; water is extra, not a replacement.
For more on cups, see cups and dropping bottles.
Do I need to boil water for my baby?
Advice on boiling differs between countries.
| Source | What it says |
|---|---|
| Pregnancy, Birth and Baby (AU) | Boil and cool tap water for babies until 12 months; boil tank water too |
| NHS (UK) | Drinking water for babies over 6 months doesn't need to be boiled |
| AAP and CDC (US) | The pages we checked don't give boiling advice for drinking water |
If you're in the US, or you use tank, bore or well water anywhere, ask your GP, child-health nurse or local water authority what's right for your supply.
Pregnancy, Birth and Baby describes how to prepare tap water safely:
- Use an electric kettle and let it boil until it switches off — or on a stovetop, bring water to a rolling boil (it keeps boiling when you stir it).
- Let it cool to a safe temperature before giving it to your baby.
- Store cooled boiled water in a clean, sterilised bottle in the fridge.
It also says store-bought bottled water should only be used if the bottle hasn't been opened or damaged, and once your baby is 12 months old you no longer need to boil tap water.
How much water should a toddler drink?
After 12 months, water and milk become the main drinks. The AAP suggests:
| Age | Water a day (AAP) |
|---|---|
| 6–12 months | 4–8 oz (½–1 cup) |
| 12–24 months | 8–32 oz (1–4 cups) |
| 2–5 years | 8–40 oz (1–5 cups) |
The AAP notes that fluoridated tap water helps prevent tooth decay. Offer water with meals and snacks. The NHS suggests offering sips of water with meals rather than squash for older children. For milk after 12 months, see moving to cow's milk.
Why shouldn't babies have juice or other drinks?
All three countries agree that babies under 12 months don't need juice. The AAP says infants under 1 year should not drink juice at all, because it's very sweet, lacks fibre, raises the risk of tooth decay, and can make it harder to later prefer plain water. The NHS says babies under 12 months don't need fruit juice or smoothies, and if older children have them they should be diluted (1 part juice to 10 parts water) and kept to mealtimes to reduce tooth decay.
Pregnancy, Birth and Baby lists drinks that aren't recommended for babies under 12 months:
- juices
- tea and coffee
- soft drinks, cordials and other sugar-sweetened drinks
- cow's, goat's and sheep's milk as a drink
- plant-based milks such as oat, coconut, rice and almond
- mineral water
The NHS adds that squash isn't suitable for young babies, fizzy drinks shouldn't be given to babies and young children, and children under 5 shouldn't have rice drinks as a substitute for breast milk.
How do I know my baby is getting enough fluid?
Pregnancy, Birth and Baby says a baby is well hydrated if they have 6 to 8 wet nappies with pale urine over 24 hours. Fewer wet nappies than usual is a reason to offer more feeds and get medical advice the same day (see below). See signs of dehydration.
When a baby has a fever, Pregnancy, Birth and Baby suggests:
- Under 6 months: offer extra breastfeeds, or the usual amount of formula.
- Over 6 months: keep breast or formula feeding, and you can also offer water or an oral rehydration solution.
It notes many babies eat less when unwell, which is fine as long as they're getting enough fluids. Any fever in a baby under 3 months needs urgent care — see below and our fever guide.
If you're keeping a log, jot down wet nappies and drinks on hot or sick days. A count across 24 hours is far more useful to a nurse or doctor than a guess.
When should I get help?
Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now if your baby has had no wet nappy or wee in 12 hours, is floppy, difficult to wake or can't be woken, has a seizure, is struggling to breathe, or has blue, grey or blotchy skin or lips. The NHS guide to serious illness lists these as emergencies, along with a temperature of 38°C (100.4°F) or higher in a baby under 3 months. If a baby under 6 months has been given a lot of water and becomes very sleepy, floppy or has a seizure, call your local emergency number (000 in Australia, 999 in the UK, 911 in the US).
Get medical advice today (call a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US) or see a GP) if your baby stops breast or bottle feeding while unwell, has fewer wet nappies than usual, or keeps vomiting and can't keep fluids down — the NHS vomiting guide lists these for an urgent call.
Ask your GP or child-health nurse about water if your baby was premature, has a medical condition, or you've been given different advice for your baby.
