Newborn & everyday care

Why is my baby’s poo green?

An unexpected nappy colour can leave you wondering what has changed. Here is a calm guide to what to look for, what feeding can change and when to ask for help.

When to get medical help

Green poo is not the same as green vomit. Call 999 or go to A&E if your baby has yellow-green or green vomit. Get emergency help for severe breathing difficulty or a baby who is not responding normally.

Call NHS 111 if your baby stops breast or bottle feeding while ill, has fewer wet nappies, cannot keep fluids down or has bloody diarrhoea.
If your baby is under 12 months and you are worried about diarrhoea or vomiting, call NHS 111. You do not need to wait for symptoms to become severe.

Why a nappy may look green

In the first days after birth, poo changes as the early, sticky meconium passes. Green can be part of this transition.

Some infant formula milks can make poo green. Starting solid foods, usually around six months, also changes its colour. An otherwise well baby who is feeding and growing normally may simply have an occasional green nappy.

What changes in the first week?

Newborn nappies offer useful clues about feeding. These are general patterns, not a diagnosis from a single nappy.

Days 1–2: the first poo, called meconium, is usually sticky and dark green or black.
Days 3–4: poo becomes softer and may look brown, green or yellow.
Days 5–6: poo is usually yellow. Speak to your midwife or health visitor if nappies are not changing as expected or you are worried about milk intake.

Look at feeding, not colour alone

Breastfed poo is often loose and seedy; formula-fed poo is commonly firmer. If breastfeeding feels difficult or you are unsure about attachment, ask your midwife or health visitor to watch a feed.

If your baby has diarrhoea or vomiting, continue breast or bottle feeds. Smaller, more frequent feeds may help if they are being sick. Do not dilute formula.

What else should I check?

Look beyond the shade of green: is your baby feeding as usual, having wet nappies and behaving like themselves? Tell your GP or health visitor about changes in consistency, smell or comfort too.

Green and watery, with unsettled behaviour or less interest in feeds: speak to your GP or call NHS 111.
White, grey or very pale poo: contact your GP to get it checked.
Red poo or possible blood: contact your GP. Bloody diarrhoea needs NHS 111 advice.
Black poo after the first five days: get it checked by your GP, rather than assuming it is still meconium.

You can ask for reassurance

If you are uncertain, contact your midwife or health visitor about feeding and nappies. Use your GP or NHS 111 for an unwell baby or urgent concerns. You know your baby, and it is reasonable to ask for help even when you cannot put your finger on what feels different.

About this guide

Written by Floreo using the NHS sources below, checked on 9 October 2026. This is general information, not a diagnosis or personalised medical advice. It is not NHS-approved or endorsed and has not been independently clinically reviewed.