Blood in a baby’s poop can look surprisingly different depending on where it comes from. It might show up as bright red streaks on the outside of the stool, tiny dark flecks mixed in, or a deep maroon-to-black color throughout. Some parents expect to see obvious red liquid, but blood in infant stool is often subtle, and several harmless things can mimic it.
Bright Red Streaks or Flecks
The most common appearance is bright red streaks or small flecks on the surface of the stool. This typically means the blood is coming from somewhere near the end of the digestive tract, most often from a tiny tear in the skin around the anus called an anal fissure. These tears happen when a baby passes a hard or large stool, and the blood ends up on the outside of the poop rather than mixed into it. You might also notice a small amount of bright red blood on the diaper itself.
Babies with a sensitivity to cow’s milk protein can also have small streaks or flecks of blood in their stool. In this case, the blood tends to appear alongside mucus, giving the poop a slightly slimy quality. The baby usually looks perfectly healthy otherwise, which is one reason this condition can catch parents off guard. It shows up most often between one and four weeks of age in breastfed babies whose mothers consume dairy, or in formula-fed babies on a cow’s milk-based formula.
Dark Red, Maroon, or Black Stool
When blood has traveled through more of the digestive system before coming out, it gets darker. Dark red or maroon-colored poop suggests bleeding from higher up in the intestines. Black, tarry stool (outside of the first few days of life, when dark meconium is normal) points to bleeding even further up, potentially from the stomach, esophagus, or throat. The blood turns black because stomach acid breaks it down during digestion.
One common and completely harmless cause of dark stool in newborns is swallowed maternal blood. During delivery, babies can swallow small amounts of blood, and breastfed babies sometimes ingest blood from cracked or bleeding nipples. Swallowed maternal blood typically shows up as black or tarry stool, or as maroon-colored streaks in the meconium. If your pediatrician suspects this, a lab test can confirm whether the blood belongs to the mother or the baby.
Stool Mixed With Blood and Mucus
A distinctive and more urgent pattern is stool that looks like dark red jelly, sometimes described as “currant jelly” because of its color and texture. This is a mix of blood and mucus, and it can signal a condition called intussusception, where one section of the intestine slides into another like a telescope. Intussusception cuts off blood flow to part of the bowel and requires emergency medical care. It’s most common between 6 months and 3 years of age and usually comes with intense, cramping belly pain that makes a baby pull their knees up, followed by periods of calm between episodes.
Bacterial infections from organisms like Campylobacter, Salmonella, or Shigella can also produce bloody, mucus-filled diarrhea. Research has found that about one in ten newborns with bloody stools had a bacterial cause, which is higher than many clinicians expect. These infections usually come with fever, frequent watery stools, and a baby who seems generally unwell.
Things That Look Like Blood but Aren’t
Not every red or dark spot in a diaper is blood. Several common substances can cause convincing lookalikes:
- Urate crystals. Newborns sometimes leave a reddish-orange, powdery residue in their diaper that looks alarming but is simply concentrated uric acid from the urine. When the diaper dries, it leaves behind a fine rust-colored powder. This is normal in the first few days of life and usually resolves as the baby starts feeding well.
- Foods. Once babies start solids, beets, blackberries, and foods with red dye can turn stool pink or red.
- Certain antibiotics. A common antibiotic prescribed for ear infections can turn stool bright red or maroon when it reacts with iron in formula. The stool looks dramatic but tests negative for actual blood. Babies on this medication have no stomach symptoms and are otherwise fine.
- Iron supplements or iron-fortified formula. These often turn stool dark green or black, which can be mistaken for digested blood.
How to Tell What You’re Seeing
Color and location give you the most useful clues. Bright red blood sitting on top of a formed stool, especially if the baby strained, most likely comes from a small anal tear. Flecks or streaks mixed into loose, mucousy stool in an otherwise healthy young infant point toward a milk protein sensitivity. Black, tarry stool in a newborn who recently breastfed from a mother with cracked nipples is likely swallowed maternal blood.
If you’re unsure whether what you see is actually blood, save the diaper. Your pediatrician can test the stool with a simple chemical screening that detects hidden blood, even amounts too small to see clearly. This takes the guesswork out of it entirely.
Signs That Need Immediate Attention
Most causes of blood in baby stool are mild, but certain combinations of symptoms signal something more serious. A large amount of blood in the stool, or blood passed without any stool at all, warrants an emergency room visit. The same applies if your baby vomits blood.
Other warning signs to act on quickly include a baby who looks pale, limp, or unusually sleepy, has a swollen or tender belly, refuses to eat, or has a high fever alongside the bloody stool. The “currant jelly” pattern described above, especially paired with episodes of sudden crying and drawing up the legs, needs emergency evaluation because intussusception can damage the intestine within hours if untreated.
For a small streak of bright red blood in an otherwise happy, feeding baby with no other symptoms, a call to your pediatrician during regular hours is usually sufficient. They can examine the area around the anus for fissures and, if needed, test the stool to confirm what’s going on.