My Child Can't Keep Down Fluids During Stomach Flu: What to Do and When to See a Doctor

It's the middle of the night. Your child has thrown up for the third time, you've just wiped the floor again, and the moment you offer a sip of water it all comes right back up. You wonder: How am I supposed to keep her hydrated if nothing stays down — and when do I actually need A&E?

Almost every parent has been here. The most important thing first: with a stomach bug, the danger isn't the vomiting itself — it's the loss of fluid. And that loss can almost always be replaced with one simple method: tiny amounts, every minute or two. In most cases that's enough. Only a small set of clear warning signs means: see a doctor right now. Both are coming up.

Why won't my child keep any fluid down?

During a stomach bug the lining of the stomach is irritated and reacts to volume by triggering vomiting. If you offer a full glass at once, the stomach stretches and everything comes right back up. But tiny amounts can already be absorbed by the lining of the mouth and oesophagus — before they even reach the stomach.

The most common causes are viral — in infants and toddlers usually rotavirus, in older children mostly norovirus. Both are highly contagious and tend to cause a short, intense episode with vomiting first and diarrhoea afterwards. After 2–3 days the worst is usually over.

That's why parents so often feel: "Nothing at all stays in." In reality, more stays in than it feels — if the method is right. So the key isn't how much your child can drink at once, but how often and how slowly.

What signs of dehydration mean I need a doctor right now?

These signs mean your child may already be significantly dehydrated and needs medical help today — GP, NHS 111, or A&E. If several of these signs appear together: call 999 or go straight to A&E.

In babies under 3 months, vomiting or diarrhoea needs urgent medical advice — contact a GP or call NHS 111 straight away (call 999 or go to A&E if your baby seems seriously unwell).

These warning signs follow NHS guidance. You don't need to memorise all of them — but any single one is reason enough to seek medical help. Better to call too early than too late.

How do I actually get fluids into my child?

The standard rule is surprisingly simple: very small amounts, very often. In practice that means: as soon as your child has stopped throwing up, give one teaspoon of fluid every 1–2 minutes. For children who refuse the spoon, an oral syringe (no needle) often works better. This avoids the "full glass, all comes up" effect.

Choose the right fluid

The NHS recommends an oral rehydration solution (ORS) — electrolyte-glucose sachets you mix with water, from a pharmacy. It's the best-studied option scientifically. It replaces not only water but also the salt lost through vomiting and diarrhoea. For mild cases, diluted tea with a pinch of salt and some glucose is also accepted.

What you should not give:

• Soft drinks (cola, soda, iced tea) — too much sugar, makes diarrhoea worse
• Pure fruit juice — irritates the gut and can trigger vomiting
• Salty pretzels alone — the old home remedy doesn't replace a real ORS
• Plain tap water in large amounts — can throw off salt balance in small children

How much is enough?

As a rough guide — orientation, not a strict rule — after every loose stool or vomit, replace with 50–100 ml in infants and 100–150 ml in toddlers, given spoonful by spoonful over several minutes — never all at once. If your child is already showing signs of dehydration, this is a job for your GP — they'll set the exact amount.

Breastfed babies: keep nursing

For breastfed babies the answer is simple: nurse more often, in shorter sessions. Breast milk already contains the ideal mix of water and electrolytes. The NHS recommends putting breastfed babies to the breast more frequently to cover their increased fluid needs — no pause, no extra tea, just keep nursing.

When can I just watch and wait?

If your child is older than 3 months, awake and responsive, peeing regularly, and small sips are staying down, the situation is usually not acute. You watch at home — most stomach bugs settle on their own within 2–3 days and need no medication.

Still, keep an eye on the trajectory. Note roughly how often your child has vomited or had diarrhoea, when they last drank, and how many wet nappies (or, for older kids, bathroom trips) you've counted. These running notes help you spot a downward turn early.

When a call to your GP the next day is the right move:

• Diarrhoea lasting longer than 2–3 days without improvement
• Infant with more than 4 watery stools in 24 hours, toddler with more than 6, school-age with more than 8–10
• Refusing to drink for more than 8 hours (infant) or more than 1 day (toddler)
• Belly pain that doesn't ease
• Visible weight loss — even a few hundred grams in small children is meaningful

These thresholds aren't red-alert — they're prompts: time to ask for medical advice before "just taking a while" becomes real dehydration.

What if there's fever along with the stomach bug?

Fever combined with vomiting and diarrhoea adds significantly to fluid loss — through the skin and faster breathing. NHS guidance lists fever combined with vomiting and diarrhoea as a combination that warrants seeing your GP. Even without classic dehydration signs, the threshold is lower in this combination.

How to handle it

1. Lower threshold for a call: With fever + vomiting + diarrhoea, call your GP sooner rather than later — even if your child seems otherwise stable.
2. Liquid fever meds may not work: If your child is throwing up everything, oral fever syrup is often pointless. Suppositories may be the better choice. More on this in our article on fever in children.
3. Drinking before lowering temperature: Rehydration takes priority over reducing fever. A child who drinks copes better with 39 °C than a child at 38.5 °C who is drying out.

Frequently asked questions about stomach flu in children

How long does a stomach bug usually last in a child?

Most viral gastrointestinal infections clear within 2–3 days, some a little longer. Vomiting often improves within 24 hours, while diarrhoea may linger a bit. If vomiting or diarrhoea lasts longer than 2–3 days, or gets worse rather than better, it's time to call your GP.

Should I give my child soft drinks or salty pretzels?

No. That old home remedy is outdated. Soft drinks have too much sugar and can make diarrhoea worse. Salty pretzels alone don't provide a balanced electrolyte mix. What's actually recommended: an oral rehydration solution (ORS) from the pharmacy — or, for mild cases, diluted tea with a pinch of salt and some glucose.

My baby spits up a lot — is that already a stomach bug?

Not every spit-up is real vomiting. Babies often bring up small amounts of milk after feeds — that's normal as long as they're gaining weight and feeding well. Forceful, projectile vomiting that doesn't stop, or green or bloody vomit, are warning signs. For babies under 3 months, the rule is: when in doubt, call your GP early.

When can my child go back to nursery after a stomach bug?

Rule of thumb: 48 hours without vomiting or diarrhoea, then nursery is usually fine. Some reportable pathogens (like norovirus or EHEC) require longer waiting periods. When in doubt, ask your GP or nursery. After: thorough hand hygiene at home, since some pathogens stay infectious for days.

Should I offer food while nothing is staying down?

Not at first. The first 4–6 hours are about drinking only — calming the stomach and replacing fluids. Once your child can keep several sips down, offer light foods like rusks, grated apple, or banana. A long "diet" isn't necessary — NHS guidance even recommends returning to normal eating once rehydration is achieved.

My child has diarrhoea but no vomiting — is that worth tracking?

Yes, absolutely. Note the frequency, consistency, and rough volume. The thresholds for a doctor's visit depend on age: infants from 4 watery stools per day, toddlers from 6, school-age children from 8–10. More tips on what to do when diarrhoea and vomiting last several days — once the acute phase has passed.

What's the best fluid to give during a stomach bug?

The first choice is an oral rehydration solution (ORS) from the pharmacy — it replaces water, sodium, and glucose in the right ratio. For mild cases, diluted lightly sweetened tea (chamomile, peppermint, weak black tea) is an alternative. Avoid pure juice and soft drinks — they make diarrhoea worse.

Summary: Won't keep fluids down — what now?

The shortest decision rule:

Situation	What to do
Baby < 3 months with vomiting or diarrhoea	Urgent — NHS 111 / GP straight away (999 if seriously unwell)
Sunken eyes, sunken fontanelle, lethargy, blood in vomit/stool	Call 999 or go to A&E
No tears, dry mouth, no urine in > 8 hours	See your GP today
Fever > 39.5 °C plus vomiting	See your GP today
Vomiting > 4 hours, nothing stays down	Call NHS 111
Diarrhoea > 2–3 days, refusing fluids > 8 h (baby)	See your GP soon
Child awake, responsive, peeing, sips staying down	Spoon-rehydrate, observe

Drinking strategy at a glance

This flowchart applies to repeated vomiting during a stomach bug. In infants, occasional spit-up after feeding or vigorous play (upside-down positions) is usually normal and not a sign of illness.

What to keep an eye on over the next hours

What to watch	When it gets serious
Wet nappies / urination	Infant: no wet nappy in 8 h. Toddler: no urine in 8 h
Tears when crying	No more tears → fluid deficit
Mouth and lips	Dry lips, sticky mouth → call your GP
Alertness / responsiveness	Apathetic, hard to wake → call 999
Breathing	Fast and deep through mouth → see your GP today