Why is my baby's poop green?

The most common cause is a foremilk/hindmilk imbalance in breastfed babies - baby gets more thin foremilk than fatty hindmilk. Other normal causes include iron-fortified formula, starting green vegetables, teething, or a mild stomach bug. Green poop alone is rarely a reason to call the doctor.

Is green baby poop normal?

Yes, in the vast majority of cases. Green poop is normal in breastfed and formula-fed babies for many reasons. The time to call your pediatrician is if green poop comes with mucus that persists more than 2 days, blood, fever over 100.4°F, or signs of dehydration.

Can iron in formula cause green poop?

Yes, and this is very common. The iron in iron-fortified formula can turn poop a dark greenish color. This is completely normal and healthy - your baby needs that iron for brain development. There's no need to switch formulas.

What does green mucus in baby poop mean?

Persistent green, mucusy poop - especially with specks of blood, eczema, or unusual fussiness - can indicate a food sensitivity, often to dairy or soy. For breastfed babies, this may mean something in mom's diet. Talk to your pediatrician if it persists for more than 2 days.

Does teething cause green poop?

It can. Many parents and some pediatricians report looser, sometimes greener stools during teething. The leading theory is that excess swallowed saliva speeds up digestion. It usually resolves when the tooth breaks through and shouldn't be severe diarrhea.

Green Baby Poop: 7 Common Causes and What to Do

You opened the diaper and it's green. Maybe bright green, maybe dark green, maybe green with some interesting textures. Your first instinct is to panic. Your second instinct should be to read this article.

In the vast majority of cases, green baby poop is completely normal. Here are the 7 most common causes.

1. Foremilk/Hindmilk Imbalance

The #1 cause of green poop in breastfed babies. When baby gets more foremilk (the thinner, lactose-rich milk at the start of feeding) and less hindmilk (the fattier milk), the result is green, sometimes frothy poop.

Fix: Let baby fully drain one breast before switching to the other.

2. Iron-Fortified Formula

Iron in formula can turn poop a dark greenish color. This is completely normal and not a reason to switch formulas. Your baby needs that iron for brain development.

Fix: No fix needed! This is healthy.

3. Starting Green Foods

Peas, spinach, kale, avocado, green beans - when these hit your baby's digestive system, they come out looking pretty much the same color they went in.

Fix: No fix needed. It means baby is eating their greens!

4. Teething

Many parents notice green, looser stools during teething episodes. The theory is that excess saliva swallowed during teething speeds up digestion.

Fix: This usually resolves when the tooth breaks through.

5. Stomach Bug

A mild viral illness can speed up digestion, resulting in green stools. If baby has a cold or mild tummy bug, green poop is a common side effect.

Fix: Keep baby hydrated. It should resolve in a few days.

6. Food Sensitivity or Allergy

Persistent green, mucusy poop - especially with blood specks, eczema, or unusual fussiness - can sometimes indicate a food sensitivity (often dairy or soy in mom's diet for breastfed babies, or in formula). Learn more in our guide to milk protein allergy and baby poop.

Fix: Talk to your pediatrician. They may recommend an elimination diet or formula change.

7. Medications

Certain antibiotics and medications can change poop color to green. If baby recently started any medication, this is likely the cause.

Fix: Usually resolves when the medication course ends.

When Green Poop IS a Concern

Green poop alone is rarely worrying. For full context on what different colors mean, see our baby poop color chart. But see your pediatrician if green poop comes with:

Visible blood or mucus that persists for more than 2 days
Fever over 100.4°F (38°C)
Refusing to eat or significant weight loss
Severe diarrhea (8+ watery stools per day)
Signs of dehydration (fewer wet diapers, no tears, sunken fontanel)

Track It With PipPoopie

Instead of trying to remember whether yesterday's poop was "more green" or "less green," let PipPoopie track it for you. Our AI analyzes each diaper photo, tracks color changes over time, and alerts you to patterns that might matter. It's the difference between guessing and knowing.