Black Poo in Babies: Causes and When to Worry | Parenting Hub
Once meconium has cleared, black poo can be from iron supplements or from upper-gut bleeding. Here's how to tell them apart.
Newborn meconium is meant to be black. After day 5, true black poo needs a closer look — iron drops are the usual cause, but bleeding has to be ruled out.
Common (and harmless) causes
- Iron supplements or iron-fortified formula — common, harmless
- Foods with dark colour (blueberries, liquorice) once on solids
- Swallowed blood from a cracked nipple while breastfeeding — looks dark
When black is serious
True 'melaena' — black, tarry, sticky and foul-smelling poo — can mean bleeding from the upper gut (stomach, oesophagus). It's not common in babies but always needs same-day medical review.
What to do
If your baby is on iron, the cause is almost certainly that. If they're not on iron and you don't recognise it as a food, see your GP today (or after hours).
When to seek help
- Black, sticky, tarry poo with foul smell
- Vomiting blood or coffee-ground vomit
- Pale, floppy or unsettled baby with black poo — ED now
Common questions
Could swallowed blood from breastfeeding cause this?
Yes — a small amount can darken poo. If your nipples are bleeding or cracked, see an IBCLC. Persistent dark poo still warrants a GP review.