My infant has grass‑colored (green) stools; is this normal or a sign of a problem, and what symptoms would require medical evaluation?

Green Stools in Infants: Normal Variation

Green-colored stools in healthy infants are a normal finding and do not require medical evaluation in the absence of other concerning symptoms. Nearly half (47.4%) of healthy term infants experience green stool as the dominant color for at least one week during the first 17 weeks of life, with comparable frequency in both breastfed (47.7%) and formula-fed (45.2%) infants 1.

Normal Stool Color Patterns in Infancy

• Yellow and light brown are the most common stool colors in healthy infants, but green stools occur frequently as a normal variation 1
• Green stools are associated with higher defecation frequency (more rapid intestinal transit), which is a benign physiological finding 1
• At 3 months of age, 50% of formula-fed infants have green-colored stools, which should be considered completely normal 2
• Breastfed infants typically have more yellow-colored stools than formula-fed infants, but both groups commonly experience green stools 2

When Green Stools Require Medical Attention

Seek immediate medical evaluation if green stools are accompanied by:

• Bilious (dark green/yellow-green) vomiting - this indicates intestinal obstruction and requires urgent surgical evaluation for possible malrotation with volvulus 3, 4
• Blood in the stool (though occasional blood occurs in 9.3% of healthy infants and is often benign) 1
• Signs of dehydration including decreased urine output (fewer than 4 wet diapers in 24 hours), dry mucous membranes, or poor skin turgor 4
• Poor weight gain or failure to thrive 4
• Projectile or persistent vomiting 4
• Abdominal distension or tenderness 3
• Lethargy or altered mental status 5

Reassurance for Parents

• Green stools alone, in a well-appearing infant who is feeding normally and gaining weight appropriately, require no intervention 1, 2
• The color variation reflects normal differences in intestinal transit time and bile metabolism, not disease 1, 2
• Both breastfed and formula-fed infants experience green stools with similar frequency, so changing feeding methods is unnecessary 1

Important Distinction: Green vs. Acholic (Pale) Stools

• Pale, clay-colored, or white stools are abnormal and may indicate biliary obstruction (such as biliary atresia), requiring immediate evaluation 6
• Green stools are distinctly different from acholic stools and should not be confused with the pale, discolored stools that warrant urgent investigation 6