GUIDE
In the first 2-3 days? Totally normal — it's meconium. After the first week? Call your pediatrician.
Black stool in newborns is expected and healthy. Black stool in older babies is a different story. This guide walks you through what causes dark and black poop at every age, when it's harmless, and when it needs a doctor's attention.
Black poop in a baby tells one of two very different stories, and the dividing line is simple: how old is your baby?
In the first two to three days of life, black stool is not just normal — it's expected. This is meconium, your baby's very first bowel movement, and every newborn passes it. Meconium is thick, sticky, tar-like, and dark black or very dark green. It's made up of amniotic fluid, skin cells, mucus, bile, lanugo (fine body hair), and other materials your baby swallowed while in the womb. It has almost no odor because it's not digested food — it's essentially a collection of everything that was floating around in there for nine months.
After the first week of life, the story changes completely. By day five, your baby's stool should have transitioned from black meconium through dark green transitional stool to its mature color — mustard yellow for breastfed babies, yellow-tan for formula-fed babies. If black, tarry stool appears after this transition is complete, it's no longer meconium. It could be iron-related (harmless) or it could be melena — digested blood from the upper gastrointestinal tract (needs medical attention).
The rest of this guide helps you tell these scenarios apart, understand what's happening in each case, and know exactly when to call your pediatrician.
| Cause | Age | Appearance | Normal? | What to Do |
|---|---|---|---|---|
| Meconium | First 2-3 days | Thick, sticky, tar-like, odorless | Yes — expected first stool | No action needed. Should transition to green, then yellow by day 5. |
| Transitional stool | Days 3-5 | Dark green to greenish-brown, less sticky | Yes — transition phase | Normal progression from meconium to mature stool. No action needed. |
| Iron-fortified formula | Any age on formula | Dark green to greenish-black, paste-like | Yes — from iron | Expected with iron-fortified formula. Do not switch formulas for this reason alone. |
| Iron drops/supplements | Any age on supplements | Very dark green to black, may stain | Yes — from iron | Expected side effect of iron supplementation. Continue as prescribed. |
| Blueberries or dark foods | 6+ months (on solids) | Dark purple to near-black, may have chunks | Yes — diet-related | Check what baby ate in the last 24 hours. Blueberries are the usual suspect. |
| Melena (digested blood) | Any age after newborn period | Black, tarry, sticky, strong foul odor | No — needs evaluation | Call your pediatrician immediately. May indicate upper GI bleeding. |
Meconium is one of those things nobody really warns you about before you have a baby, and then suddenly you're staring at a diaper that looks like someone spilled roofing tar in it and wondering if this is normal. It is.
Your baby has been practicing swallowing in the womb for months, taking in amniotic fluid along with skin cells, mucus, bile salts, and fine body hair called lanugo. All of that material accumulates in the intestines and forms meconium. It's sterile — no bacteria have colonized your baby's gut yet — which is why it has almost no smell.
Most babies pass their first meconium within the first 24 hours of birth. It continues for another day or two, sometimes with multiple meconium diapers in a single day. The consistency is thick, sticky, and genuinely difficult to clean up. It clings to skin. It stains. It's the kind of substance that makes you immediately understand why diaper cream was invented.
Pro tip: Apply a thin layer of petroleum jelly or coconut oil to your baby's bottom before the first meconium diaper. This creates a barrier that makes cleanup dramatically easier. Hospital nurses often share this trick, but it's worth knowing in advance.
By days three to five, meconium begins to transition. The stool lightens from black to dark green to greenish-brown to greenish-yellow, and then finally settles into your baby's mature stool color. This transition is actually an important clinical sign — it tells your medical team that your baby is taking in milk and processing it. If stool hasn't begun lightening by day four or five, mention it to your pediatrician or lactation consultant, as it could indicate that baby isn't getting enough milk.
| Timing | What You'll See | Details |
|---|---|---|
| Birth to 24 hours | First meconium passed | Most babies pass meconium within the first 24 hours. Thick, black, tar-like, nearly odorless. |
| 24-48 hours | Continued meconium | May still be dark black. Multiple meconium diapers are normal in this window. |
| Days 2-3 | Transitional stool begins | Color shifts from black to dark green. Less sticky, slightly looser. Meconium mixing with digested milk. |
| Days 3-4 | Greenish-brown to greenish-yellow | The transition is clearly underway. Stool is lighter, less tarry, more 'normal' looking. |
| Day 5+ | Mature stool color | Mustard yellow (breastfed) or yellow-tan (formula-fed). Meconium phase is complete. |
All of these are common, harmless causes of dark stool. No action needed.
After meconium, the most common cause of dark stool in babies is iron — either from iron-fortified formula or from iron drops prescribed by your pediatrician.
Iron is an essential mineral for your baby's development. It's critical for brain development, oxygen transport in the blood, and healthy growth. The AAP recommends that all formula-fed babies receive iron-fortified formula and that exclusively breastfed babies begin iron supplementation at around four months of age, when their iron stores from birth start to deplete.
When your baby takes in iron, not all of it is absorbed. The unabsorbed iron passes through the digestive system and is excreted in stool. As it moves through, it oxidizes — the same chemical reaction that makes iron rust — and turns the stool dark green, greenish-black, or even black. This is purely cosmetic. The dark color doesn't mean anything is wrong; it just means the iron is passing through.
The important thing is to distinguish iron-related dark stool from melena (digested blood). Here's how:
If your baby is taking iron and has dark stool with no other symptoms — eating well, gaining weight, not fussy — it's almost certainly the iron. If you're ever uncertain, your pediatrician can run a simple fecal occult blood test (a stool sample on a card) to check for hidden blood. It takes seconds and provides a definitive answer.
Log every diaper change in tinylog with color notes. When you have a week of data showing 'dark green, iron formula' as the pattern, you won't panic on Tuesday. And if something genuinely changes, you'll see it clearly.
Let's be direct about this: black, tarry stool that appears after the meconium period and isn't explained by iron supplements needs to be evaluated by your pediatrician. The medical term for this is melena, and it can indicate bleeding in the upper gastrointestinal tract — the stomach or upper small intestine.
When blood is digested as it passes through the GI tract, it turns black and tarry. This is different from seeing red blood in the stool (which usually comes from the lower GI tract — a fissure, for example). Melena has a very characteristic appearance: jet black, sticky, and tar-like, with a distinctly foul odor that's noticeably different from regular stool.
Causes of upper GI bleeding in infants can include:
The most important thing to know is this: if your baby has black, tarry stool after the newborn period and they are not on iron supplements, call your pediatrician the same day. Don't wait for the next scheduled visit. It may turn out to be something benign — swallowed maternal blood is common and harmless — but it needs to be evaluated.
Save the diaper or take a clear photo. Your pediatrician will want to see it and will likely want to test the stool for blood.
Any of these warrants a prompt call to your pediatrician. And as always: white, pale, or chalky stool is a separate emergency that requires immediate medical attention regardless of age.
Once your baby starts solids around six months, a new and entirely harmless cause of dark stool enters the picture: food.
Blueberries are the most common culprit. They can produce stool that looks genuinely black or very dark purple, and if you've forgotten what your baby ate yesterday (understandable — you're tired), the diaper can be startling. Blackberries, dark cherries, grape juice, and even beets (which can produce dark reddish-black stool) can have similar effects.
Other foods that can darken stool include:
The diagnostic trick here is simple: think back 12-24 hours. If your baby ate something dark-colored and the stool is dark but otherwise normal in consistency and odor, it's almost certainly diet-related. If you remove the suspected food from their diet and the dark stool clears up within a day or two, you have your answer.
However, if dark stool persists after eliminating potential dietary causes, or if it's accompanied by symptoms like fussiness, vomiting, or a foul odor that's different from normal stool, call your pediatrician.
Iron is critical for your baby's brain development, oxygen transport, and growth. The AAP recommends iron-fortified formula for all formula-fed babies and iron supplementation for exclusively breastfed babies starting at 4 months. Dark stool is a cosmetic side effect of iron passing through the body. It is not harmful.
Iron-related dark stool is dark green to greenish-black and has a consistency similar to your baby's normal stool — just darker. Melena (digested blood) is truly black, has a distinctive tar-like stickiness, and smells noticeably foul — different from regular stool odor. If you're unsure, call your pediatrician. They can do a simple stool test to check for hidden blood.
Some parents stop giving iron drops or switch to a non-iron formula because of dark stool. Don't do this without consulting your pediatrician. Iron deficiency in infancy can have lasting effects on cognitive development. The dark stool is harmless — the iron deficiency is not.
Iron drops can stain teeth, lips, and clothes. Give them with a syringe toward the back of the mouth, followed by a few sips of water or milk. Some parents give iron drops right before a feed so the milk rinses the residue. Check with your pediatrician about the best timing.
Before your baby's first meconium diaper, apply a thin layer of petroleum jelly or coconut oil to their bottom. Meconium is notoriously sticky — like trying to clean up tar — and the barrier cream makes it wipe off much more easily. Your postpartum nurse may tell you this, but if they forget, you'll thank yourself later.
If your baby is on iron drops or iron-fortified formula and you see dark stool, the iron is almost certainly the explanation. It helps to know this so you don't panic every time. If you switch to a different formula or stop iron drops and the dark stool continues, that's when it's worth a call to your doctor.
This sounds unpleasant, but it's genuinely useful. Meconium has almost no smell. Iron-related dark stool smells like regular stool — not great, but not alarming. Melena (digested blood) has a very distinctive, sharp, foul odor that's different from normal poop. If the dark stool smells truly terrible in a way you haven't encountered before, call your pediatrician.
Dark stool can look very different depending on the lighting. What looks black under a dim bathroom light might actually be dark green or dark brown in natural daylight. If you're concerned, take a photo near a window and show it to your pediatrician. They'll be able to tell a lot from a good photo.
For a complete overview of what every poop color means — not just dark and black — see our baby poop color chart. And if green is the color that's got you searching, we have a dedicated green baby poop guide as well.
This guide is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your pediatrician or healthcare provider with any questions about your baby's health. If you see black, tarry stool after the meconium period that is not explained by iron supplementation, contact your pediatrician promptly. If you see white, pale, or chalky stool at any time, seek immediate medical attention.
