Water Intoxication in Babies Under 6 Months
Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist
Content reviewed against published AAP, CDC, WHO guidelines
Last reviewed:
If your baby has been diagnosed with or you suspect water intoxication in babies under 6 months, here is what the evidence says.
The short answer
Babies under 6 months should not be given plain water. Their immature kidneys cannot process extra water, which dilutes sodium in the blood (hyponatremia) and can cause seizures, brain swelling, and in rare cases can be fatal. Breast milk or properly prepared formula provides all the hydration a young baby needs, even in hot weather.
Key takeaways
- Babies under 6 months should not be given plain water. Their immature kidneys cannot process extra water, which dilutes sodium in the blood (hyponatremia) and can cause seizures, brain swelling, and in rare cases can be fatal. Breast milk or properly prepared formula provides all the hydration a young baby needs, even in hot weather.
- Usually normal when: Your baby over 6 months takes a few sips of water with meals — this is safe and appropriate
- Call your doctor if: Your baby under 6 months consumed a significant amount of plain water and is showing symptoms such as irritability, drowsiness, swelling of the face, low body temperature, or seizures — call 911 immediately
- Varies by age — see the age-by-age breakdown below
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What Parents Should Know
According to AAP, CDC, WHO guidelines, babies under 6 months should not be given plain water. Their immature kidneys cannot process extra water, which dilutes sodium in the blood (hyponatremia) and can cause seizures, brain swelling, and in rare cases can be fatal. Breast milk or properly prepared formula provides all the hydration a young baby needs, even in hot weather. At 0-6 months, this is the critical period when water intoxication is a real danger. Never give plain water to a baby this age, even in small amounts. Do not dilute formula beyond manufacturer instructions. In hot weather, offer more frequent breast or formula feeds instead of water. Even a few ounces of water can be dangerous for a small baby because their kidneys are not mature enough to excrete the excess fluid. It is generally considered normal when your baby over 6 months takes a few sips of water with meals — this is safe and appropriate. However, you should contact your pediatrician promptly if your baby under 6 months consumed a significant amount of plain water and is showing symptoms such as irritability, drowsiness, swelling of the face, low body temperature, or seizures — call 911 immediately.
Normal vs. Concerning
By Age
What to expect by age
0-6 months
This is the critical period when water intoxication is a real danger. Never give plain water to a baby this age, even in small amounts. Do not dilute formula beyond manufacturer instructions. In hot weather, offer more frequent breast or formula feeds instead of water. Even a few ounces of water can be dangerous for a small baby because their kidneys are not mature enough to excrete the excess fluid.
6-12 months
Once your baby starts solid foods around 6 months, small sips of water with meals are safe — typically 2-4 ounces per day. Water should complement, not replace, breast milk or formula. Avoid giving large amounts of water at once. If your baby seems excessively thirsty, offer breast milk or formula first.
12 months+
After 12 months, your toddler can drink water more freely as their kidneys are more mature. Water becomes an important part of hydration alongside whole milk and solid foods. There is still no need to force large quantities, but the risk of water intoxication is much lower at this age.
What to Tell Your Pediatrician
- Describe when you first noticed water intoxication in babies under 6 months and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if someone gave your baby under 6 months a small amount of water and you are concerned.
- Mention if you have been over-diluting formula and want to confirm the correct preparation ratio.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your baby over 6 months takes a few sips of water with meals — this is safe and appropriate
- Your breastfed or formula-fed baby under 6 months seems satisfied after regular feeds without added water
- You are offering extra breast or formula feeds during hot weather instead of water
- Someone gave your baby under 6 months a small amount of water and you are concerned
- You have been over-diluting formula and want to confirm the correct preparation ratio
- You are unsure when and how much water to introduce with solid foods
- Your baby under 6 months consumed a significant amount of plain water and is showing symptoms such as irritability, drowsiness, swelling of the face, low body temperature, or seizures — call 911 immediately
- Your baby has been given diluted formula over multiple feedings and seems lethargic, is vomiting, or is not acting like themselves
What You Can Do at Home
- Keep track of when you notice water intoxication in babies under 6 months — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby over 6 months takes a few sips of water with meals — this is safe and appropriate — this is generally within the range of normal.
- At 0-6 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
- While monitoring at home, seek immediate care if your baby under 6 months consumed a significant amount of plain water and is showing symptoms such as irritability, drowsiness, swelling of the face, low body temperature, or seizures — call 911 immediately.
Related Resources
Frequently asked questions
Is water intoxication in babies under 6 months normal?
When should I call the doctor about water intoxication in babies under 6 months?
When is water intoxication in babies under 6 months normal?
What causes water intoxication in babies under 6 months?
What should I mention to my pediatrician about water intoxication in babies under 6 months?
Is water intoxication in babies under 6 months normal at 0-6 months?
Is water intoxication in babies under 6 months normal at 6-12 months?
Should I go to the ER for water intoxication in babies under 6 months?
Does water intoxication in babies under 6 months go away on its own?
References
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Water Intoxication in Babies Under 6 Months.
Things to mention
- Describe when you first noticed water intoxication in babies under 6 months and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if someone gave your baby under 6 months a small amount of water and you are concerned.
- Mention if you have been over-diluting formula and want to confirm the correct preparation ratio.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- Someone gave your baby under 6 months a small amount of water and you are concerned
- You have been over-diluting formula and want to confirm the correct preparation ratio
- You are unsure when and how much water to introduce with solid foods
Urgent signs to report immediately
- Your baby under 6 months consumed a significant amount of plain water and is showing symptoms such as irritability, drowsiness, swelling of the face, low body temperature, or seizures — call 911 immediately
- Your baby has been given diluted formula over multiple feedings and seems lethargic, is vomiting, or is not acting like themselves
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members
Related Resources
Bottom line
Most cases of water intoxication in babies under 6 months are normal. Talk to your pediatrician if your baby under 6 months consumed a significant amount of plain water and is showing symptoms such as irritability, drowsiness, swelling of the face, low body temperature, or seizures — call 911 immediately.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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