Green poop is often caused by leafy greens, food coloring, or food moving quickly through the gut. See a doctor if it persists.
Common causes
- Green leafy vegetables (spinach, kale).
- Green food coloring.
- Iron supplements.
- Diarrhea or fast transit: bile hasn’t turned brown yet.
- Antibiotics.
Babies
Green stool is common in infants.
Illness
Infections like Giardia or salmonella and conditions like IBS or celiac can cause green diarrhea.
When to see a doctor
Green stool lasts more than a few days, or comes with diarrhea, fever, blood or pain.
Normal
Stool color varies from brown to green depending on diet and bile.
Black or red
Black or bloody stool needs urgent evaluation.
Why stool turns green
Stool gets its brown color from bile pigments that are chemically changed as bile passes through the intestine. If food moves too quickly, bile has less time to change, and stool can stay green.
Food and supplement causes
- Leafy greens such as spinach, kale and broccoli.
- Green food coloring in drinks, candies, frosting and ice pops.
- Blue or purple foods, like blueberries and some sports drinks.
- Iron supplements, though these usually make stool dark green or black.
- Chlorophyll and spirulina supplements.
Medical causes
- Diarrhea or rapid transit.
- Antibiotics, which change gut bacteria.
- Gastrointestinal infections like salmonella.
- Celiac disease, Crohn’s disease and irritable bowel syndrome.
- After gallbladder removal, bile can reach the intestine more continuously.
Infants
Green stool is common in babies. Newborn meconium is dark green to black in the first days. Breastfed infants and those taking iron fortified formula can also have green stool.
How long is normal
A single green stool after a salad is normal. Many people go back to usual color within a day or two after the cause is removed.
Call a doctor if
- It lasts more than a week or two without explanation.
- It comes with fever, severe cramps, vomiting, blood or dehydration.
- Watery diarrhea persists beyond 2 days in adults, or 24 hours in infants.
Red flags of other colors
Black, tarry stool can mean bleeding in the upper digestive tract, red stool can mean bleeding in the lower tract, and pale or clay colored stool can signal a bile duct issue. These need medical evaluation.
How stool gets its color
Stool is brown because red blood cells break down into bilirubin, which gut bacteria convert into stercobilin. If food moves quickly through the colon, bile stays green and the stool appears green. Typical gut transit takes 24 to 72 hours, and diarrhea shortens it. Green foods such as spinach, kale, broccoli, green beans, blueberries with dye and foods with green coloring produce green stool. Iron supplements can give a dark green to black color. Antibiotics change gut bacteria, which can alter color.
When it matters
Green stool alone with no other symptoms and lasting a day or two is normal. See a doctor if it lasts more than a few days, or comes with diarrhea, abdominal pain, fever or weight loss. Stomach infections, celiac disease, Crohn disease and irritable bowel syndrome may cause rapid transit. Black tarry stool, bright red blood or pale clay colored stool can signal bleeding or liver and bile duct issues and need prompt medical attention. In infants, green stool is common in the first days (meconium) and with formula or iron fortified products. Keep track of diet, medications and symptoms to help the doctor.
Based on data from the Mayo Clinic and the NIDDK
