Baby Poop (UK): A Colour-by-Colour Guide to What's Normal
Few things send a new parent to Google faster than an unexpected colour in the nappy. Green? Mustard? Almost black? This is a calm, UK guide to what baby poo actually tells you — how it changes in the first days, what's normal for a breastfed versus formula-fed baby, why green is usually nothing to worry about, and the handful of colours that genuinely need checking. The reassuring headline: baby poo comes in a wide range of normal colours, and most of what surprises you is completely fine. There are just three colours worth acting on — and we'll make those easy to spot.
What's normal changes fast in the early days
Newborn poo transforms almost by the day in that first week — so what looks alarming on day two can be textbook. Here's the usual journey:
- Meconium (first 24–48 hours): sticky, dark greenish-black and tar-like — almost like engine oil. It's the material baby built up in the womb, and it's a good sign when it passes.
- Transitional (around day 3–5): as your milk comes in, poo turns greenish-brown and looser. This is the changeover stage and it's completely normal.
- Breastfed baby: soft to runny, mustard-yellow, often with a "seedy" or grainy look and a mild, not-unpleasant smell.
- Formula-fed baby: firmer and more paste-like, paler tan-to-brown, with a stronger smell. Formula-fed babies also tend to be a bit more regular.
- Weaning: once solids begin, poo becomes thicker, browner and considerably smellier — and undigested bits and surprise colours (sweetcorn, blueberries, tomato) are normal. More on that below.
If you're still finding your feet with nappies in general, our guide to how many nappies a baby should have pairs nicely with this one.
Baby poo colour chart
Here's the quick reference. Most colours sit firmly in the "usually fine" group. Only three — white, red and black — belong in the "get it checked" group.
| Colour | What it usually means |
|---|---|
| Normally fine | |
| Mustard-yellow | Classic breastfed poo — soft, seedy, mild. Perfectly normal. |
| Tan / pale brown | Typical formula-fed poo — firmer and pastier. Normal. |
| Green | Usually normal — fast transit, foremilk/hindmilk balance, or just a colour. No need to panic. |
| Brown | Normal, and increasingly the standard once weaning begins. |
| Dark greenish-black (first days only) | Meconium — expected in the first 24–48 hours. |
| Get it checked | |
| Pale, chalky or white | Can signal a liver problem — speak to a GP or health visitor promptly. |
| Red (fresh blood) | Blood in the poo should always be checked — contact your GP or NHS 111. |
| Black or tarry (after the meconium days) | Can indicate old blood — get it checked promptly. |
Keep this simple in your head: white, red and black are the three to act on. Everything else on the yellow–green–brown spectrum is almost always part of normal variation.
Green baby poo: usually nothing to worry about
Green is the colour that panics parents most, and it's almost always fine. Common, harmless reasons include food moving quickly through the gut (fast transit), the balance of foremilk and hindmilk in a breastfed baby, a bit of a cold or teething, or simply that particular day's colour. A green nappy in a baby who is feeding well, weeing plenty and generally content is not a red flag. If green poo comes with lots of very watery stools, a poorly baby, or it's persisting and you're worried, that's worth a chat with your health visitor — but green on its own is not a reason to panic or to change what you're doing.
How often should a baby poo?
There's a huge normal range, and it shifts with age and how baby is fed:
- Newborns (especially breastfed): often poo several times a day — sometimes with nearly every feed in the early weeks.
- After about 6 weeks: a breastfed baby can go several days — sometimes up to a week — between poos and still be perfectly fine, as long as the poo is soft when it comes and baby is comfortable and content.
- Formula-fed babies: tend to be more regular, usually at least once a day, and their poo is firmer.
What matters is the pattern for your baby, and that poo stays soft and comfortable to pass. For a fuller picture of nappy output by age — including the wet nappies that reassure you feeding's going well — see our nappies-by-age guide. And if you're still building feeding rhythm, the newborn feeding schedule gives helpful context.
Baby poo when weaning
Starting solids changes everything about the nappy — and it's meant to. Expect poo to become thicker, browner, firmer and much smellier. You'll also see undigested food: whole peas, sweetcorn kernels, a red tinge after tomatoes or beetroot, or dark bits after blueberries. This is completely normal and doesn't mean anything's wrong — little tummies simply don't break everything down yet. Weaning can also make some babies a little more prone to constipation as their gut adjusts, so keep offering water with meals. Our weaning schedule guide walks through the whole first-foods journey if you're just getting going.
Red flags: when to get baby poo checked
Most of the time, colour is nothing to worry about. But a few signs do warrant a call — please don't wait on these:
- Pale, chalky or white poo — this can be a sign of a liver problem and should be checked promptly.
- Red blood in the poo — fresh red streaks or blood should always be checked with your GP or NHS 111.
- Black, tarry poo after the meconium days — once the first few days are past, black poo can indicate old blood and needs checking.
- Signs of dehydration or a very unwell baby — far fewer wet nappies, a sunken soft spot, no tears, unusual sleepiness or a baby who just isn't themselves.
In short: white, red or black poo should be checked promptly — contact your GP or NHS 111, and call 999 if your baby is seriously unwell. Acting quickly here is exactly the right instinct.
Constipation: hard, pellet-like poo
Constipation shows up as hard, dry, pellet-like poos, straining and obvious discomfort, and sometimes a firmer tummy. It's more common in formula-fed babies and once weaning starts. What can help: offering cooled boiled water between feeds (for formula-fed babies), gentle tummy massage and bicycle legs, and — for weaning babies — more water and fruit and veg. Always make up formula exactly to the instructions, never adding extra powder. See your GP or health visitor if it doesn't settle, if there's blood from straining, or if your baby seems in real pain.
Diarrhoea: watery, more frequent poo
Diarrhoea means poo that's much more watery and more frequent than usual for your baby. The main thing to watch for is dehydration, especially if it comes alongside vomiting — keep offering feeds, as milk is the best fluid for young babies. Contact NHS 111 or your GP if diarrhoea is persistent, contains blood, comes with a high temperature, or if you notice signs of dehydration such as fewer wet nappies. Trust your instincts: a baby who seems genuinely unwell always deserves a call.
How CubTrack helps
When it comes to nappies, the reassurance is almost always in the pattern — but patterns are impossible to hold in your head at 3am on no sleep. CubTrack's nappy tracker lets you log each wet and dirty nappy in a tap, noting the colour and consistency, so you build a clear history over time. That means you can show your health visitor or GP exactly what's been happening rather than trying to remember, and you can spot changes early — a run of harder poos, a gap that's stretching, or a colour worth mentioning. Both parents log to the same shared record, so whoever does the change, nothing gets lost. Download CubTrack free on iOS or Android.
This is general guidance, not medical advice. Babies vary enormously — trust your instincts and speak to your health visitor or GP if you're ever worried.
Baby poop FAQs
Is green baby poo normal?
Yes — green baby poo is usually completely normal. It can come from food moving quickly through the gut, the foremilk/hindmilk balance in breastfed babies, teething or a mild cold. If your baby is feeding well and content, green on its own isn't a cause for concern.
What colour baby poo is a red flag?
White, red and black are the three to act on. Pale or chalky white poo can signal a liver problem, red means blood, and black or tarry poo (after the first few days of meconium) can mean old blood. Get any of these checked promptly with your GP or NHS 111.
What does newborn meconium look like?
Meconium is sticky, dark greenish-black and tar-like, and it's passed in the first 24–48 hours. It's the material your baby built up in the womb, and passing it is a healthy sign. After a few days it gives way to greenish-brown transitional poo.
How is breastfed baby poo different from formula-fed?
Breastfed poo is typically soft to runny, mustard-yellow, seedy and mild-smelling. Formula-fed poo is firmer and pastier, paler tan-to-brown, and stronger-smelling. Both are perfectly normal — they simply look different.
How often should my baby poo?
It varies hugely. Newborns, especially breastfed, may poo several times a day. After about six weeks a breastfed baby can go several days between poos and still be fine, as long as it's soft and they're content. Formula-fed babies tend to be more regular.
Why does my baby's poo have bits of food in it after weaning?
Undigested food such as sweetcorn, peas or blueberry skins is completely normal once weaning starts. Little tummies don't break everything down yet, so bits and surprise colours pass straight through. It's nothing to worry about.
Worried about a colour or a change? See the whole picture instead of guessing. Get CubTrack free on Android, log every wet and dirty nappy in a tap, and keep a clear history to share with your health visitor or GP.
