The short answer
Babies younger than six months who get enough breast milk or correctly prepared formula generally do not need extra drinking water, even in hot weather. From around six months, offer a few sips with solid foods without replacing milk feeds.
In this guide · 11 sections
Keep in mind
- Do not routinely offer plain water before six months.
- 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 Organization (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 the breast when your baby asks, seek shade, avoid overheating, and choose light clothing. If you use formula, do not dilute it or introduce additional water on your own. If your baby feeds poorly, has a fever, or has fewer wet diapers, contact a healthcare professional rather than assuming it is only the heat.
Is it different if your baby uses formula?
Routine extra water is not recommended before six months for formula-fed babies either. Infant formula is designed to be prepared with a specific ratio of water to powder. The thought of making it “a little thinner so baby stays hydrated” is understandable but unsafe.
Follow the exact preparation directions on the formula container. 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 diapers, overall behavior, 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.
With your baby sitting upright and supported, offer a few sips from a small open cup while you stay close. You do not need to increase water or decrease milk abruptly on their six-month birthday. CDC guidance for ages six to twelve months mentions about 4–8 fluid ounces (120–240 mL) daily; it does not apply to four- or five-month-olds and is not a quota to meet.
How can you tell whether your baby is hydrated?
Perhaps your baby nursed less than usual today and you noticed lighter diapers. One less-wet diaper does not by itself establish dehydration, but a clear change over the day deserves attention.
Look at wet diapers 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, diarrhea, 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 diarrhea 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. If they are not yet six months old, keep up breast milk or correctly prepared formula rather than adding a daily water bottle. On a hot day, prioritize a cooler environment, feeding cues, and wet diapers.
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 color, seizures, or unresponsiveness: call 911.
- Marked dehydration signs, repeated choking, or persistent swallowing concerns require medical advice.
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
- American Academy of Pediatrics / HealthyChildren — How to Safely Prepare Baby Formula With Water
- CDC — Foods and Drinks to Encourage
- CDC — When, What, and How to Introduce Solid Foods
- Centers for Disease Control and Prevention (CDC) — Foods and Drinks for 6 to 24 Month Olds
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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