Few parenting topics become interesting as quickly as the inside of a nappy.
Baby poo can change colour, texture and frequency across the first days, weeks and months. It can also change with breast milk, formula, solids, medicine, a cold, or a normal shift in routine. That does not make every change a problem, but it can make it hard to know what to ignore, what to write down, and what to ask about.
This chart is for calm observation. It cannot tell you what is causing a colour change, and it does not replace advice from a GP, health visitor, doctor or paediatrician.
Baby poo colour chart
| Colour | What it can mean | What to do |
|---|---|---|
| Black or very dark green in the first days | This is often meconium, your baby’s first poo. NHS-linked guidance says this usually appears in the first 24 to 48 hours. | Keep an eye on the normal transition towards green, then yellow or mustard. |
| Yellow or mustard | Common for breastfed babies. It may look loose, seedy or runny. | Usually one to log as normal if your baby is otherwise feeding and well. |
| Brown, tan or orange | Common for formula-fed babies and babies eating solids. Formula poo may be firmer and smellier than breastfed poo. | Usually one to log as normal if it fits your baby’s usual pattern. |
| Green | Can happen with formula, some foods, slow digestion, illness, or normal variation. | If your baby seems well and is feeding, a one-off green nappy is often not urgent. Log it and watch the pattern. |
| Red | Red or blood-streaked poo can be food-related once solids are introduced, but it can also be blood. | Discuss this promptly with a healthcare professional, especially if there is any doubt or your baby is not eating red foods. |
| Pale, white or grey | Pale or white poo can be a warning colour. | Contact a health visitor, GP, doctor or paediatrician for advice. |
| Black after the first week | Black poo after the meconium phase can sometimes suggest bleeding. | Seek medical advice. |
| Very watery, very smelly, or suddenly much harder than usual | This can matter, especially if your baby seems unwell, has fewer wet nappies/diapers, or the change does not settle. | Speak to a health visitor, GP, doctor or paediatrician. |
Is green baby poo normal?
Green baby poo or poop can be normal, especially if it happens once and your baby seems otherwise well. Formula can sometimes make poo look darker green, and switching from breastfeeding to formula can also make poo darker.
What matters is the whole picture: feeding, wet nappies or diapers, temperature, behaviour, whether your baby seems uncomfortable, and whether the colour keeps happening.
Instead of trying to decide what green poo means on its own, it can help to log:
- the colour
- whether the poo was watery, loose, soft, hard or sticky
- what your baby had been fed
- whether there were symptoms such as fever, vomiting, poor feeding or unusual sleepiness
- whether the colour happened once or repeatedly
When does meconium change?
Meconium is usually sticky and black-green. Over the first few days, it commonly moves towards green, then yellow or mustard as milk feeding becomes established.
If your newborn does not pass meconium in the expected early window, or if you are worried about feeding, wet nappies or jaundice, speak to your midwife, health visitor, GP or baby’s doctor.
How feeding can change poo colour
Feeding method affects both colour and texture.
Breastfed babies often have yellow or mustard poo that can be runny and not very smelly. Formula-fed babies often have darker, firmer and smellier poo. When solids begin, nappies may become browner, thicker and more varied.
That does not mean one feeding method is better based on poo colour. It just means the nappy is part of the wider feeding picture.
For more detail, see How feeding influences your baby’s poo.
What should you record?
You do not need a perfect nappy diary. A short note is usually enough:
Wednesday morning: green, loose poo. Formula feed earlier. Baby feeding normally and settled after.
Or:
Friday evening: pale-looking dirty nappy. Called health visitor for advice.
Acornio is designed to keep these small details together: stool colour, consistency, food or feed context, symptoms and notes. The aim is not to diagnose anything. It is to help you remember what happened and prepare a clearer conversation if you need one.
When to speak to a GP or paediatrician
Speak to a health visitor, GP, doctor or paediatrician if:
- your baby’s poo is pale, white or grey
- red, blood-streaked or black poo appears, or you are unsure whether food explains the colour
- poo becomes very watery, very smelly or repeatedly hard
- your baby seems unwell, unusually sleepy, feverish, dehydrated, or is feeding poorly
- you are worried, even if you are not sure why
If symptoms feel sudden, severe or serious, seek urgent medical help.