25 October 2026 · Samantha Lin
Designer · Mother of two
Baby Diarrhoea: How to Tell It From Normal Loose Poop
Diarrhoea in a baby isn't loose poop. A breastfed baby's poop is meant to be loose, sometimes after every feed, and the WHO says plainly that loose, pasty stools in a breastfed baby don't count as diarrhoea. Diarrhoea is a change: stools that suddenly come much more often than her usual, turn watery and get bigger, sometimes soaking into the diaper instead of sitting on top of it.
The first thing a doctor will want to know is what's normal for her, and it helps to know that before you need it. For the first month with Richard I kept a note on my phone: the time, the feed, wet or dirty, and a word about colour. It felt obsessive at the time. It also meant that when he had his first tummy bug, I could tell our GP in Punggol what his usual was and what had changed in two sentences, and she could get on with examining him.
Her normal, and what counts as a change
| Normal for many babies | Looks like diarrhoea | |
|---|---|---|
| How often | Her usual number, which for a breastfed newborn can be every feed | Suddenly much more often than her usual |
| Texture | Soft, runny or seedy, sitting in the diaper | Watery, soaking into the diaper, sometimes leaving a wet ring |
| Amount | Her usual | Bigger, often leaking out at the legs or back |
| Smell | Her usual | Often stronger, or different |
| The baby | Feeding, wetting diapers, content | May be off her feeds, unsettled, feverish or vomiting |
The AAP describes diarrhoea in babies as a watery stool that can come up to 12 times a day. NICE, the body that writes the UK's clinical guidelines, tells doctors to suspect a stomach bug when a child's stool suddenly turns loose or watery. In both, the key word is sudden.
Count the wet diapers
The poop tells you something's wrong, and the wet diapers tell you how much it matters. Babies dehydrate faster than older children, and NICE lists the ones at higher risk: under a year old and particularly under six months, small at birth, more than five watery stools or more than two vomits in the last 24 hours, or a baby who's stopped breastfeeding while ill. Fewer wet diapers is one of the first signs the NHS lists for young children. A dry diaper after a long nap is the one to notice. The AAP says to call the doctor if a baby with diarrhoea hasn't passed urine for three hours or more. Watery poop can make it hard to tell a wet diaper from a dirty one, so if you can't tell, count it as dirty and keep looking for one that's clearly wet. Write each one down.
Keep feeding, at full strength
Keep breastfeeding, and feed more often if she'll take it, which is SingHealth's advice for babies under a year. Keep formula going too, made up exactly as the tin says. The NHS says to use it at its usual strength, and NICE tells doctors to give full-strength milk straight after a child has been rehydrated. Watering formula down doesn't rest her stomach. It just puts less food in the same bottle.
Don't swap her milk for plain water. SingHealth says not to give babies water alone, and KidsHealth adds fruit juice, soft drinks and sports drinks to the list to avoid. Diarrhoea medicine from the pharmacy isn't for babies either: NICE says not to use it in children under five, and SingHealth says the medicines adults take to stop diarrhoea aren't used in children.
Oral rehydration solution, with a doctor's say-so
Oral rehydration solution, the sachets and bottles sold at pharmacies, replaces the water and salts that diarrhoea takes out. The WHO calls it the main treatment, and NICE uses it to rehydrate children unless they need a drip. For a baby, though, how much and how often is a question for a doctor or pharmacist, since it depends on her weight and how dry she already is. The AAP warns against making your own, because a homemade mix may not have the right balance of salts. Ask before you start, and ask how to give it if she's vomiting as well.
Her poop, the rest of the time
Fever, vomiting, blood or mucus
These change the picture. NICE lists the signs that should make a doctor think beyond an ordinary stomach bug: a temperature of 38°C or higher in a baby under three months, or 39°C or higher from three months, blood or mucus in the stool, green vomit, a swollen or very painful tummy, a bulging soft spot, a rash that doesn't fade when pressed, and fast or laboured breathing. Any of those needs a doctor, not a wait-and-see.
See a doctor the same day if any of these apply.
- She's three months old or younger.
- Her temperature is 38°C or more.
- She's vomiting, or can't keep fluids down.
- She's refusing feeds, or she's irritable and not herself.
- Fewer wet diapers than usual, or no wee for three hours or more.
- Blood or mucus in the stool, or stool that's black.
- The diarrhoea is still going after seven days.
In Singapore, KK Women's and Children's Hospital on Bukit Timah Road and NUH at Kent Ridge both run children's emergency departments around the clock, and 995 is the number for an ambulance. Our GP has seen both boys through tummy bugs, but with a floppy baby at three in the morning I wouldn't wait for a clinic to open.
What to photograph and write down
A doctor can't see a diaper from yesterday, and "a lot" means different things at 4am. Before you leave the house, or while you're waiting to be seen, put these in your phone.
- A photo of a dirty diaper in daylight or under a white light, with the inside of the diaper in the shot.
- How many dirty diapers since it started, and when the last clearly wet one was.
- Her feeds: how much, how often, and whether she's taking less than usual.
- Her temperature, and the time you took it.
- Any vomiting: how many times, and what colour.
- Whether anyone at home, at infant care or at the grandparents' has had the same thing, and any recent travel.
If there's blood, mucus or a colour you can't name, bring the diaper too, sealed in a bag, because phone cameras are poor at colour under yellow light. Don't hold up a trip to A&E for any of this.
Afterwards
NICE says diarrhoea from a stomach bug usually lasts five to seven days in young children and has stopped within two weeks in most. Keep her home from infant care until 48 hours after the last bout of diarrhoea or vomiting, which is also NICE's advice, and wash your hands well after every change. Her bottom will probably be sore by the end of it. I'm not sure either of mine got through a bout without a rash, and the fix both times was plain water, a soft cloth and a thick layer of barrier cream at every change.
For the sore bottom
Mentioned above
Asked at the playground
How do I know if my baby has diarrhoea or just loose poop?
Look for a change from her normal: stools that are suddenly much more frequent, watery and bigger than usual, often soaking into the diaper. Loose, pasty stools in a breastfed baby are normal and aren't diarrhoea.
Should I keep breastfeeding or giving formula when my baby has diarrhoea?
Yes. Keep breastfeeding, more often if she'll take it, and keep giving formula made up at its usual strength. Don't dilute formula or replace milk with plain water, juice or sports drinks.
Can I give my baby oral rehydration solution?
Oral rehydration solution is the standard treatment for dehydration, but ask a doctor or pharmacist how much to give a baby. Don't make it at home, since the salt balance may be wrong.
When is baby diarrhoea an emergency?
Go to A&E or call 995 if she's very sleepy or floppy, pale, mottled or cold, breathing fast or with effort, vomiting green, or has a rash that doesn't fade under a glass. See a doctor the same day if she's under three months, feverish, vomiting, refusing feeds, has fewer wet diapers or has blood in the stool.
What I read for this
- NICE CG84: Diarrhoea and vomiting caused by gastroenteritis in under 5s, recommendations
- NHS: Diarrhoea and vomiting
- American Academy of Pediatrics: Diarrhea in babies
- World Health Organization: Diarrhoeal disease fact sheet
- SingHealth: Diarrhoea, childhood illnesses
- KidsHealth (Nemours): Diarrhea
- KK Women's and Children's Hospital: Children's Emergency
- National University Hospital: Children's Emergency
This guide is general information, written to help you understand a topic and ask better questions. It is not medical advice and does not replace your own doctor, midwife or paediatrician. Anything that worries you about your baby belongs with them.