How do I know if my baby is dehydrated?

The clearest signs are fewer wet diapers (fewer than 6 in 24 hours, or none for 8–12 hours), no tears when crying, a dry mouth, a sunken soft spot, and unusual sleepiness. A well-hydrated baby keeps wetting diapers and makes tears. Any severe sign needs a call to your pediatrician.

Should I give my baby Pedialyte or water?

For a baby under 1 year, breast milk or formula comes first; if those won't stay down, an oral rehydration solution like Pedialyte is the next step. Avoid giving plain water as the main fluid to infants — it can dilute their salts. Plain water and diluted juice are fine for children over 1.

When is vomit color a warning sign?

Green or yellow (bile-stained) vomit and any blood in vomit are red flags — call your pediatrician right away, as they can signal a blockage or other serious problem. Plain milky spit-up or stomach-bug vomit without those colors is far less concerning, though still worth watching for dehydration.

How long does a stomach bug last in a baby?

Vomiting usually settles within a day or two, while diarrhea from a virus can last 5 to 14 days as the gut heals. If diarrhea lasts longer than 2 weeks, or your baby can't keep fluids down, contact your pediatrician for evaluation.

Health & Safety

Baby Vomiting and Diarrhea: When to Worry

Worry mainly about dehydration: call your pediatrician if your baby has fewer than 6 wet diapers in 24 hours, no tears when crying, a dry mouth, or a sunken soft spot, or seems unusually sleepy. Most vomiting and diarrhea comes from a passing stomach bug that clears on its own. The danger isn't the bug itself — it's losing too much fluid, which happens fast in babies.

6 min read Health & Safety Updated June 2026

What's usually behind it

The most common cause of vomiting and diarrhea in babies is viral gastroenteritis — the "stomach flu" — usually from norovirus or rotavirus. It typically brings a day or so of vomiting followed by several days of loose, watery stools, sometimes with a low fever. Viral diarrhea can last 5 to 14 days as the gut recovers.

Your job during a stomach bug is to keep fluids going in faster than they come out, watch closely for dehydration, and know the small list of signs that mean something more serious than a typical bug.

Signs of dehydration by level

Dehydration can move from mild to severe quickly in babies. Severe signs need a doctor now.
Sign	Mild to moderate	Severe — call now
Wet diapers	Fewer than usual	Fewer than 6 in 24 hours, or none in 8–12 hours
Mouth and lips	Slightly dry	Very dry, cracked
Tears	Fewer tears	No tears when crying
Soft spot (fontanelle)	Normal to slightly flat	Clearly sunken
Behavior	A little fussy or tired	Very sleepy, hard to wake, limp
Eyes	Normal	Sunken

How to rehydrate your baby

Give small amounts often — small sips beat large feeds that come right back up. Aim for at least 1 ounce (30 mL) of fluid per hour.

Under 6 months: keep breastfeeding or formula-feeding as usual, in smaller, more frequent amounts. Do not give plain water to young infants.
6 months to 1 year: offer undiluted breast milk or formula first; if that isn't staying down, use a commercial oral rehydration solution (such as Pedialyte or Enfalyte). Still avoid plain water as the main fluid.
Use a teaspoon, medicine cup, or syringe to give a little every few minutes if your baby won't take a bottle.
Wait about 15–20 minutes after a vomit, then restart with tiny sips and build up slowly.
Over 1 year: an oral rehydration solution, or diluted apple juice (half water, half juice), is fine. Skip full-strength juice, sports drinks, and soda — the sugar can worsen diarrhea.
Don't withhold food once vomiting settles; offer normal feeds and easy foods as your baby is ready.

What not to do

Don't give plain water as the main drink to a baby under 1 year — it can throw off their salt balance. Skip full-strength fruit juice, sports drinks, and sodas, which pull more water into the gut and make diarrhea worse.

Don't give anti-diarrhea or anti-vomiting medicines to babies unless your pediatrician specifically tells you to; several are unsafe for young children. And don't wait out clear dehydration or any red flag below — babies can decline quickly.

Call your pediatrician or seek care if

Your baby is 3 months old or younger and has vomiting, diarrhea, or any fever.
There's blood or mucus in the stool, or vomit that is green/yellow (bile) or bloody.
No wet diaper for 8 to 12 hours, or other signs of dehydration in the table above.
Your baby is very sleepy, limp, hard to wake, or won't take any fluids.
Vomiting is forceful and repeated, or paired with a swollen, hard, or very painful belly.
Diarrhea is severe, or lasts longer than 2 weeks.
There's a high fever, or your baby just seems to be getting worse.

Reflects AAP HealthyChildren oral-rehydration guidance and Cleveland Clinic / Nemours dehydration guidance, 2024-2026.

Sources & further reading

ParentFlow: one free app, newborn to age six

ParentFlow is a free baby tracker that logs feeds, sleep, diapers, pumping and growth in one tap, with your daily summary, trends, and reminders based on your own logs. Free for everyday tracking on iPhone, Android, and the web.

App Store Google Play Open Web App

This article reflects current AAP, CDC, FDA, and other public-health guidance and is for educational purposes only. It does not constitute medical advice. ParentFlow is a wellness companion — not a substitute for your pediatrician. For any medical concern, contact your healthcare provider.