The short answer
Fully breastfed babies under six months do not need additional water, even during hot weather. NHS guidance allows small sips of cooled boiled water for formula-fed babies in hot weather, alongside usual feeds. Offer sips with meals from around six months.
In this guide · 11 sections
Keep in mind
- Exclusively breastfed babies under six months need no extra water; NHS notes a hot-weather exception for formula-fed babies.
- Breast milk and correctly prepared formula provide fluid.
- Never add extra water to powdered formula.
- Around six months, offer a few supervised sips with meals.
Why do four- and five-month-olds not need extra water?
Smacking their lips at four months or wanting to feed often on a hot day does not necessarily mean your baby needs water. At this age, breast milk or age-appropriate infant formula is their main drink. For a healthy baby who feeds well, offering a separate bottle or cup of water is not a routine part of care.
The World Health Organisation (WHO) recommends exclusive breastfeeding for the first six months, without other drinks, including water. Breast milk contains the water a baby needs. Correctly prepared formula also provides fluid; do not add water separately unless your baby’s clinician gives individual instructions.
What if your baby seems thirsty in hot weather?
After coming indoors on a summer day, you might notice sweat on your baby’s neck or back and wonder whether to offer a sip of water. Exclusively breastfed babies younger than six months do not need extra water, even when it is hot. They may simply want to breastfeed more often.
Offer more breastfeeds in hot weather, keep your baby in the shade, and dress them lightly. The NHS says that formula-fed babies under six months may need small sips of cooled boiled water in hot weather alongside their usual milk feeds. Do not dilute formula, and ask your health visitor or GP if your baby feeds poorly, has a fever, or has fewer wet nappies.
Is it different if your baby uses formula?
Formula-fed babies still receive their usual fluids from correctly prepared first infant formula. Routine water in place of formula is not appropriate. However, NHS guidance makes a limited exception for small sips of cooled boiled water during hot weather for formula-fed babies younger than six months.
Follow the exact preparation directions on the formula packaging. Extra water can reduce the nutrients your baby receives and cause dangerous changes in water and electrolyte balance. Ask your child’s healthcare professional if you are concerned about how much formula your baby drinks.
Can water replace a milk feeding?
Water is an ordinary drink for adults, but during the first months milk supplies both fluid and nutrients for growth. A bottle of water can fill a baby’s small stomach while providing none of the energy and nutrients in breast milk or formula.
Your baby may then be less interested in their next milk feeding. Do not regularly replace milk with water. To judge whether your baby is feeding well, consider their wet nappies, overall behaviour, and growth pattern rather than crying or how quickly a bottle empties alone.
How do you offer water around six months?
When your developmentally ready baby starts solid foods at about six months, you can offer a little drinking water with a meal. Early sips may be more about learning to use a cup than satisfying thirst. There is no reason to insist if your baby is not interested.
After solids begin, offer sips of water from a cup with meals, as NHS guidance advises. Breast milk or first infant formula should remain your baby’s main drink during the first year. There is no need to measure a target amount.
How can you tell whether your baby is hydrated?
Perhaps your baby nursed less than usual today and you noticed lighter nappies. One less-wet nappy does not by itself establish dehydration, but a clear change over the day deserves attention.
Look at wet nappies together with alertness, a moist mouth, willingness to nurse or take formula, and their overall appearance. Clearly reduced urination, dry mouth, unusual sleepiness, or difficulty feeding warrant prompt medical assessment. Unresponsiveness, seizures, or serious breathing difficulty are emergencies.
Is plain water enough during fever, diarrhoea, or vomiting?
No. A sick infant’s fluid needs cannot be managed like thirst on an ordinary warm day. If your baby younger than six months is vomiting repeatedly, has diarrhoea or fever, or cannot feed, do not try to solve the problem by giving large amounts of plain water.
Depending on the situation, a clinician may advise more frequent milk feeds, an appropriate oral rehydration solution, or another plan. WHO makes specific exceptions to exclusive breastfeeding for medically indicated oral rehydration solutions and certain drops or syrups; these do not mean that routine drinking water should start early.
What can you do today?
Start with your baby’s age and feeding method. For babies under six months, breast milk or correctly prepared first infant formula remains the priority. On hot days, offer extra breastfeeds if wanted; the NHS allows small sips of cooled boiled water alongside normal feeds for formula-fed babies. Watch feeding and wet nappies.
If you use formula, double-check the scoop-to-water directions. If you are approaching complementary feeding at six months, having a small cup ready is enough; there is no need to make drinking a set amount of water a new achievement.
When to seek support
Some signs need emergency help; other concerns can be discussed with your child’s healthcare team.
- Trouble breathing, blue skin, seizures, or unresponsiveness: call 999.
- Contact NHS 111, your GP or health visitor for dehydration, feeding or swallowing concerns as appropriate.
Sources used for this guide
- WHO — Infant and young child feeding
- World Health Organization (WHO) — Breastfeeding – Questions and Answers
- Centers for Disease Control and Prevention (CDC) — CDC – Foods and Drinks for 6 to 24 Month Olds
- Centers for Disease Control and Prevention (CDC) — CDC – How Much and How Often to Feed Infant Formula – 21 Nisan 2026
- WHO — Exclusive breastfeeding for optimal growth, development and health of infants
- CDC — Foods and Drinks to Encourage
- NHS — How to start weaning
- NHS — Drinks and cups for babies and young children
- NHS — Your baby’s first solid foods
English editorial review:
The English text and regional guidance have been checked editorially. This is not an individual clinical assessment.
Luluna provides general parenting information. It does not diagnose conditions or replace your child’s healthcare professional.
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