Why is my newborn’s poo green?

Why is poo green in the first days?

Meconium is very dark green-black and sticky. As a baby starts taking milk, green-brown transitional stools appear; the poo then usually changes to yellow or mustard milk stool.

Around day five, if stools are still consistently dark and meconium-like, feeding, swallowing, wet nappies, and weight should be considered together, especially for a breastfed baby. Ordinary green poo later on is not the same situation.

Why is a breastfed or formula-fed baby’s poo green?

Bile pigments and the time stool takes to pass through the gut can shift its colour between yellow and green. A breastfed baby’s poo does not have to be mustard yellow every time; the shade can change even in the same day.

Formula ingredients, and iron in particular, may make poo dark green or brownish. Do not stop a prescribed iron supplement just because the stool colour changes.

Once your baby starts solids, green vegetables such as spinach or peas, and foods with green colouring, can turn poo green for a day or two. In a one-year-old who is eating and playing as usual, this is one of the most common reasons.

What does green poo not prove on its own?

Green poo alone does not show low milk supply, gas, infection, allergy, or diarrhoea. To assess milk intake, consider swallowing, feeding patterns, wet nappies, and weight gain; to assess illness, consider your baby’s overall condition and other symptoms.

It can be misleading to treat “foremilk” and “hindmilk” as two separate products and infer an imbalance from one green nappy. Do not switch breasts early, limit feeds, or remove foods from your diet because of this appearance alone.

Green poo with diarrhea, or hard and constipated?

Stool can be green during diarrhoea, but green stool is not always diarrhoea. A sudden increase from your baby’s usual frequency, with stool that is clearly more watery, is more informative.

If there is fever, vomiting, blood, lots of mucus, poor feeding, fewer wet nappies, or your baby looks unwell, do not just watch the colour. Seek advice, particularly for a baby aged 0–3 months.

Hard, dry or pebble-like poo points to constipation rather than to the green colour. It is common around starting solids or a formula change. If your baby strains in pain, there is blood on the stool, or several days pass without a stool and your baby seems uncomfortable, check in with your doctor.

Dark green or black poo: how to tell the difference

Very dark green stool may look nearly black in dim light. Checking in daylight, ideally against a white background, can help you judge the colour more accurately; remember that a photo can alter it.

After the meconium days, truly tarry, sticky black poo is not an ordinary green variation. Red or white/clay-coloured poo also needs professional assessment.

What should you watch if green poo lasts for several days?

Note when the colour began, whether feeding or formula changed, any changes in frequency or texture, and your baby’s overall condition. In a baby who feeds well, has usual wet nappies, and is growing as expected, persistent green colour alone does not prove illness.

Do not use a photo to conclude “definitely normal” or “definitely an allergy.” A photo can support observation, but clinical assessment considers age, symptoms, and growth.

What can you do today?

Check the nappy in daylight and notice whether the stool looks green or truly black.

Note the frequency and texture of the last few stools together with feeding changes and wet nappies.

If your baby seems well, do not change breastfeeding, formula, or your own diet solely because of the colour.