Blood in Baby's Stool
The short answer
Seeing blood in your baby's stool is understandably alarming, but the most common cause in young babies is a small anal fissure (a tiny tear from passing stool) or swallowed maternal blood from cracked nipples during breastfeeding. However, blood in stool always deserves medical evaluation to rule out less common but important causes like a cow's milk protein allergy or infection.
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By Age
What to expect by age
0-3 months
In newborns, the most common causes of blood in stool are swallowed maternal blood from breastfeeding and cow's milk protein intolerance, which can cause tiny streaks of blood mixed with mucus. Anal fissures from passing stool can also cause small bright red streaks on the outside of the stool. Any blood in a newborn's stool should be evaluated by your pediatrician.
3-6 months
Cow's milk protein allergy remains a common cause in this age range, affecting about 2-3% of infants. Blood may appear as small flecks or streaks mixed with mucus. If your breastfed baby has bloody stools, your doctor may suggest you eliminate dairy from your diet for 2-4 weeks to see if symptoms improve.
6-12 months
As babies start solids, constipation may lead to hard stools that cause anal fissures and bright red blood on the surface of the stool or on the diaper. Infections from bacteria like Salmonella can also cause bloody diarrhea. Intussusception, though rare, can cause currant jelly-like stools and is a medical emergency requiring immediate attention.
12-36 months
In toddlers, the most common causes of bloody stool continue to be constipation-related fissures and infectious gastroenteritis. Allergic colitis may persist or emerge. Recurrent painless rectal bleeding could indicate a Meckel diverticulum or juvenile polyp, both of which your doctor can evaluate.
What Should You Do?
When to take action
- You see a single small streak of bright red blood on the outside of a hard stool, likely from a small fissure
- Your breastfed baby has a small amount of blood in stool and you have cracked or bleeding nipples
- Your baby recently ate beets, red gelatin, or tomatoes and the stool appears reddish but is not actually blood
- You notice small streaks or flecks of blood in your baby's stool, even if your baby seems well
- Blood in stool is accompanied by mucus, suggesting possible allergic colitis or infection
- Your baby has recurring episodes of blood in stool, even if small amounts
- Your breastfed baby has persistent blood-streaked stools and you want to discuss a potential dairy elimination trial
- Your baby has large amounts of blood in the stool, bloody diarrhea, or dark red currant jelly-like stools, which could indicate intussusception or another serious condition
- Your baby has bloody stool along with vomiting, severe abdominal pain with episodes of inconsolable screaming, or lethargy
- Your baby passes black, tarry stools (not from iron supplements) which can indicate bleeding higher in the digestive tract
Sources
Related Resources
Trust your instincts. If something feels wrong, reach out to your pediatrician.
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Related Digestive Concerns
My Baby's Belly Looks Swollen
A rounded, slightly protruding belly is completely normal in babies and toddlers due to immature abdominal muscles and their proportionally larger organs. However, if the belly becomes suddenly swollen, feels hard and tight, or is accompanied by pain, vomiting, or changes in bowel movements, it needs medical evaluation as it could signal gas buildup, constipation, or rarely, something more serious.
My Baby Has an Anal Fissure (Blood When Pooping)
A small streak of bright red blood on the surface of your baby's stool or on the diaper is most commonly caused by an anal fissure, which is a tiny tear in the skin around the anus from passing hard stool. Anal fissures are very common in babies and toddlers and usually heal on their own with simple measures like keeping stools soft. While this is rarely serious, any blood in your baby's stool should be mentioned to your pediatrician.
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Silent Reflux in Baby
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Bicycle Legs Technique for Gas
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Dark Blood in Baby's Stool
Dark or black blood in stool (melena) is different from bright red blood and may indicate bleeding from the upper digestive tract (stomach or upper intestine). In newborns, black stools in the first few days (meconium) are normal. Beyond the first week, dark, tarry, or coffee-ground-like material in stool needs prompt medical evaluation. Some dark-colored foods and iron supplements can also darken stools without being blood.