Green poop is almost always harmless. The most common cause is simply eating green foods like spinach, kale, or broccoli, but it can also happen when food moves through your intestines faster than usual, preventing bile from completing its normal color change. In most cases, your stool will return to its typical brown shade within a day or two.
Why Poop Is Normally Brown
Your liver produces bile, a yellow-green fluid that helps digest fats. When bile enters your small intestine, it starts out green. As it travels through the rest of your digestive tract, bacteria and enzymes break it down into a compound called bilirubin, which gradually shifts the color from green to yellow to brown. The final brown shade you’re used to seeing is the end result of that full chemical journey. Anything that interrupts or speeds up this process can leave your stool somewhere along the green-to-brown spectrum.
Foods That Turn Stool Green
The simplest explanation for green poop is your diet. Chlorophyll, the pigment that makes plants green, can do the same to your stool when you eat enough of it. Spinach, kale, broccoli, avocados, herbs, and matcha (powdered green tea) are all common culprits. Pistachios are another one people don’t always think of, since their green color also comes from chlorophyll. Blueberries can occasionally produce greenish shades too, especially in large quantities.
Artificial food dyes are just as capable of coloring your stool. Brightly frosted cupcakes, flavored drink mixes, and ice pops can all produce unexpected shades in the toilet the next day. The dye continues tinting whatever it touches as it moves through your system. If you recently ate something with vivid coloring, that’s likely your answer.
Rapid Transit Through Your Gut
When food passes through your intestines faster than normal, bile doesn’t have enough time to fully break down. The result is stool that still carries bile’s original green tint. This commonly happens during bouts of diarrhea, whether from a stomach bug, food intolerance, or stress. You might notice your stool is both green and looser than usual, which is a strong clue that speed, not food, is the cause.
Conditions like irritable bowel syndrome or any illness that causes frequent, watery stools can produce the same effect. Once your digestion slows back to its normal pace, the brown color typically returns on its own.
Medications and Supplements
Several common over-the-counter products can turn your poop green. Iron supplements often darken stool to a deep green or even blackish-green shade. Antibiotics can disrupt the normal balance of gut bacteria, which changes how bile gets processed and can shift stool color as a side effect. Antacids containing aluminum hydroxide sometimes produce greenish poop as well.
Bismuth subsalicylate, the active ingredient in some antidiarrheal medications, reacts with sulfur in your digestive system. That chemical reaction can turn stool dark green or black. If you’ve recently started any new medication or supplement and notice the color change, the timing is probably not a coincidence.
Infections That Cause Green Stool
Bacterial and parasitic infections in the gut can produce green diarrhea, partly because they speed up transit time and partly because they trigger inflammation that changes how your intestines process bile. Infections like these usually come with other obvious symptoms: cramping, nausea, fever, or frequent watery stools. The green color alone isn’t what signals an infection. It’s the combination of color change with feeling genuinely sick that points in that direction.
Green Poop in Babies
Green stool in infants is common and usually nothing to worry about. Breastfed babies may produce green poop if they don’t finish feeding on one side before switching to the other. The earlier milk in a feeding session is lower in fat, and missing the higher-fat milk at the end can affect how the baby digests it, resulting in a green diaper. Babies who lack the typical balance of intestinal bacteria, which is normal in early life, may also have green stools.
Formula-fed babies on protein hydrolysate formula, which is used for milk or soy allergies, commonly produce green poop as well. And just like in adults, diarrhea in babies speeds up digestion enough to keep bile green. If your baby seems comfortable, is feeding well, and is gaining weight normally, green poop on its own is rarely a concern.
When Green Poop Lasts Too Long
A day or two of green stool after a big salad or a stomach bug is completely normal. If it persists for more than a few days without an obvious dietary explanation, it’s worth checking in with a healthcare provider. Green stool paired with diarrhea also raises the stakes for dehydration, especially in young children. Staying on top of fluid intake matters more than the color itself in those situations.
The color that should actually worry you isn’t green. Red or black stool (when you haven’t eaten beets or taken iron or bismuth) can indicate bleeding in the digestive tract and warrants prompt attention. White or clay-colored stool suggests a bile duct issue. Green, by comparison, sits firmly in the “probably fine” category for most people.