Green poop is almost always harmless. In most cases, it means you ate something with a lot of green pigment, or food moved through your digestive system faster than usual. Stool gets its normal brown color from bile, a digestive fluid your liver produces. Bile starts out green, and as it travels through your intestines, bacteria break it down into brown pigments. When that process gets cut short or overwhelmed by green-colored foods, the result shows up in the toilet.
Foods That Turn Stool Green
Diet is the most common reason for green poop. Chlorophyll, the pigment that makes plants green, can do the same to your stool when you eat enough of it. Spinach, kale, broccoli, avocados, fresh herbs, and matcha are frequent culprits. Even pistachios contain enough chlorophyll to shift the color. Blueberries, despite being dark blue, can occasionally produce green shades as well.
Artificial food coloring is another common cause. Brightly frosted cupcakes, flavored drink mixes, ice pops, and candy continue tinting whatever they touch as they pass through your gut. If your stool turned green a day or two after eating something with vivid dye, that’s almost certainly the explanation. The color change is temporary and clears up once the food works its way out of your system.
Medications and Supplements
Several over-the-counter products can change stool color to green or dark green. Iron supplements are a well-known one, often darkening stool and giving it a greenish hue. Antidiarrheal medications containing bismuth subsalicylate can react with sulfur in your digestive tract and produce dark green or even black stool. Antacids that contain aluminum hydroxide can cause greenish poop as a side effect.
Antibiotics deserve a separate mention. They can disrupt the normal balance of gut bacteria, and since those bacteria are responsible for converting bile from green to brown, killing them off can leave stool looking green for the duration of the course and sometimes a few days afterward.
Fast Digestion and Bile
When food moves through your intestines faster than normal, bile doesn’t have enough time to fully break down. The result is stool that retains bile’s original green color. This can happen for reasons as simple as a stomach bug, a meal that didn’t agree with you, or stress-related gut motility.
It also happens with several chronic digestive conditions. Crohn’s disease and ulcerative colitis can both speed up intestinal transit, sending bile through too quickly. Irritable bowel syndrome, particularly the diarrhea-predominant type, has the same effect. Celiac disease causes diarrhea and loose stools that are often green for the same reason. Overuse of laxatives can also push things through fast enough to keep bile green. In all of these cases, green stool is typically one symptom among others like cramping, bloating, or frequent loose bowel movements.
Green Stool in Babies
Green poop in infants is extremely common and rarely a concern. A newborn’s very first stool, called meconium, is sticky and greenish-black. During the first six weeks of life, both breastfed and formula-fed babies regularly produce stool that ranges from mustard yellow to green to brown, depending on age and feeding.
Some infant formulas specifically produce darker green stool. Breastfed babies sometimes make bright, frothy green poop, which can signal they’re getting too much of the thinner milk that comes at the start of a feeding and not enough of the richer milk that follows. Feeding from one breast at a time until it’s fully drained, rather than swapping sides mid-feed, often resolves this.
Infections That Cause Green Diarrhea
Bacterial and parasitic infections can cause green diarrhea by inflaming the intestinal lining and speeding up transit. Salmonella, commonly picked up from undercooked poultry or contaminated produce, is one of the more recognized causes. Giardia, a waterborne parasite, produces foul-smelling, greasy stools that are often green. Norovirus and other viral stomach bugs can also turn stool green simply by flushing everything through the gut before bile has time to change color.
With infections, green stool comes alongside other clear symptoms: watery diarrhea, nausea, stomach cramps, and sometimes fever. The green color itself isn’t the problem. It’s a byproduct of how quickly your body is trying to clear the infection.
When Green Stool Signals Something More
An isolated episode of green poop with no other symptoms is not a reason to worry. If you recently ate a salad, took iron pills, or had a bout of diarrhea, the color will return to normal on its own within a day or two.
Pay closer attention if green stool persists for more than a few days without an obvious dietary explanation, or if it comes with blood, severe abdominal pain, fever, or unexplained weight loss. These symptoms together could point to an inflammatory bowel condition or an infection that needs treatment. Black or tarry stool is a separate concern entirely and can indicate bleeding higher up in the digestive tract. Pale, clay-colored stool suggests bile isn’t reaching the intestines at all, which warrants prompt evaluation.
For most people, though, green poop is a one-time event with a boring explanation: you ate something green, took a supplement, or had a fast-moving digestive day. Once the cause passes, so does the color.