Vomiting, Diarrhea & Dehydration
In 10 minutes you'll know the warning signs of dehydration in a sick child, how to help them rehydrate, and which signs mean it's time for the ER.
Print this course — or save it as a PDF from the print dialog. Good for a fridge, a glovebox, or a waiting room.
Why this matters
Vomiting and diarrhea are some of the most common reasons young children need medical attention, and the real danger isn't the stomach bug itself but the fluid it takes with it. Infants and toddlers dehydrate faster than older kids and adults, according to the American Academy of Pediatrics, because their bodies hold so little fluid. Knowing the signs early lets you act before an ordinary stomach bug turns into an emergency.
Know the signs
The signs of dehydration, mild to severe
Dehydration means your child's body has lost more fluid than it has taken in, and it gets more dangerous the longer it goes on.
- Fewer wet diapers than usual — none in about 8 hours is a warning sign
- Crying without tears
- A dry mouth or dry, sticky lips
- Sunken eyes, or a sunken soft spot on a baby's head
- Being unusually tired, listless, or hard to engage
- Skin that stays tented when gently pinched, instead of springing back flat
One mild sign is worth watching closely. Several together, or any listlessness, is worth a same-day call to your child's doctor.
How to help them rehydrate
If your child is vomiting or has diarrhea but is still alert and able to swallow, offer small, frequent sips rather than a big glass at once, which can trigger more vomiting.
An oral rehydration solution — a drink made to replace lost fluids and salts — works better than water alone or sports drinks. Ask a pharmacist or your child's doctor which product and amount is right; this course teaches the idea, not a dose.
When it's the emergency room, not home care
Most stomach bugs in kids get better with rest and small sips at home. Get emergency care instead if any of these show up:
- Your child can't keep any fluid down at all, even small sips, for hours
- Vomit contains blood, or looks green or yellow-green
- Belly pain that is severe and constant, not the crampy kind that comes and goes
- Signs of more severe dehydration, like sunken eyes, no tears, or a sunken soft spot
- Your child is listless or not acting like themselves
Infants dehydrate fastest, so call your baby's doctor promptly if a baby under a year keeps vomiting or refuses fluids.
The belly pain that isn't just a stomach bug
Most vomiting in kids comes from ordinary stomach viruses. But watch for a different pattern: pain that starts near the belly button and then settles in the lower right side of the belly.
If your child's pain has moved that way, and it hurts to walk, jump, or have the area pressed, that can be a sign of appendicitis — a swollen appendix that needs surgery. This calls for a same-day medical evaluation, even if vomiting is the only other symptom so far.
Stomach bug or something worse
Most of the time, a vomiting or diarrhea illness in a child is unpleasant but not dangerous, and it runs its course in a day or two with fluids and rest.
What separates an ordinary stomach bug from an emergency isn't the vomiting count, but whether they can keep fluid down, how they look and act, and whether any sign above shows up. When you're unsure, calling your child's doctor costs nothing and never makes you the parent who overreacted.
How it really looks
No wet diaper in eight hours
Vera's one-year-old has been throwing up since the night before and hasn't had a wet diaper in almost eight hours. He's fussier than usual but still takes a spoonful of oral rehydration drink when she offers it, though some comes back up. When he cries, she notices there are no tears. Remembering that no wet diaper in about eight hours is a warning sign, she calls the pediatrician's after-hours line instead of waiting until morning. The nurse has her bring him in that evening. He's mildly dehydrated but catches up quickly on fluids, and Vera is glad she didn't wait.
The stomachache that moved to one side
Clay, 8, wakes up with a stomachache and throws up once. His dad assumes it's the stomach bug and lets him rest on the couch. By early afternoon, Clay says the pain has moved and now hurts worst on his lower right side, and he winces climbing the stairs. His dad remembers that pain settling on the lower right, especially pain that hurts to walk on, is different from an ordinary stomach bug. He calls the pediatrician, who says to come in right away. Clay is diagnosed with early appendicitis and has surgery that evening, before it can rupture.
What to do until help arrives
- Offer small sips of fluid every few minutes, rather than a large amount at once.
- Watch and count wet diapers, and note how many hours since the last one.
- Check for tears, a dry mouth, and how your child looks and acts, not just how many times they've vomited.
- Keep a bland, easy routine: let them rest, and don't force food if they don't want it.
- Note anything unusual in the vomit or stool, including blood or a green color, for the doctor.
- Call your child's doctor or an after-hours nurse line if you're unsure, especially for a baby under a year.
- Call 911 or go to the emergency room for severe constant belly pain, repeated vomiting with no fluids staying down, or a listless child.
Myths & mistakes
People often think a little vomiting means you should stop giving your child anything to drink.Actually small, frequent sips are exactly what helps, even if some comes back up. Stopping fluids makes dehydration more likely.
People often think the number of times a child has thrown up tells you how serious it is.Actually how your child looks and acts, and whether they're still making wet diapers, matters more than a count of vomiting episodes.
People often think belly pain in a child is always just a stomach bug.Actually pain that moves to the lower right side and hurts to walk or jump can be appendicitis, which needs same-day medical evaluation, not a wait-and-see approach.
What you learned
- You can spot the signs of dehydration, from fewer wet diapers to sunken eyes and tented skin.
- You know small, frequent sips of a rehydration drink help more than a big glass all at once.
- You know the emergency signs: no fluids staying down for hours, blood or green color in vomit, severe constant belly pain, or a listless child.
- You know that pain moving to the lower right side and hurting to walk can mean appendicitis, not just a stomach bug.
- You know infants dehydrate fastest, so a sick baby under a year gets a call to the doctor sooner rather than later.
Sources
- American Academy of Pediatrics — Dehydration, vomiting, and diarrhea in children: signs and home care
- Centers for Disease Control and Prevention — Diarrhea and vomiting illness in children: when to seek care
Spot an error? Tell us — accuracy matters more to us than being fast.
Common questions
How can I tell if my child is dehydrated?
Watch for fewer wet diapers than usual (none in about 8 hours is a warning sign), crying without tears, a dry mouth, sunken eyes, or a sunken soft spot on a baby's head. Unusual tiredness or being hard to engage is also a sign. One mild sign is worth watching closely; several together, or real listlessness, is worth calling your child's doctor or seeking care the same day.
What should I give my child to drink?
Small, frequent sips work better than a big glass at once, since a large amount can trigger more vomiting. An oral rehydration solution, made to replace lost fluids and salts, is generally better than water alone or sports drinks. Ask your pharmacist or child's doctor which product and amount fits your child's age and weight; this course teaches the idea, not a specific dose.
My child's stomachache moved to one side. Should I worry?
Yes, that pattern is worth same-day attention. Pain that starts near the belly button and settles in the lower right side, especially if it hurts to walk, jump, or have the area pressed, can signal appendicitis rather than an ordinary stomach bug. Call your child's doctor or seek care the same day rather than waiting to see if it passes.
Check what you know
Five questions. Four correct to pass. Retake as many times as you like — this is practice, not a test.
Keep going
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