If you notice that your poop is suddenly a shade of green, it can be alarming. However, it's usually not a major cause for concern. Olufemi Kassim, MD, a gastroenterologist at Northwestern Medicine, breaks down why it can happen.

Why Is My Poop Green?

Your Diet

• Leafy greens: Eating large amounts of leafy green vegetables like spinach, kale and broccoli can turn your stool green because of the high chlorophyll content. Chlorophyll is the pigment that gives plants their color.
• Green and blue food coloring: Artificial food coloring can contribute to green-colored stool. You often find this in candy, fruit snacks, cake frosting, freeze pops and drinks.
• Matcha: The powdered green tea matcha can cause you to see green in the toilet.
• Blue foods: Naturally blue foods like blueberries and blackberries can temporarily turn normal medium to dark brown stool green.

Medications

• Iron supplements: Iron supplements can sometimes cause your stool to darken and take on a green hue.
• Bismuth subsalicylate: Used in antidiarrheal medications, this ingredient can react to sulfur in your digestive system. When that happens, your stool may be dark green or even black in color.
• Antacids: If you are taking an antacid that contains aluminum hydroxide, a side effect can be greenish poop. 
• Antibiotics: Some antibiotics can disrupt the normal balance of bacteria in your gut. This can lead to changes in your stool color.

Infection

• Bacterial infections: In some cases, green stool can be a symptom of a bacterial infection, such as Salmonella or E. coli.
• Viral infections: Certain viral infections like norovirus (stomach flu) can cause changes in the color of your poop.

Bile

• Bile flow: Bile is a yellowish-green fluid produced by your liver and stored in your gallbladder. Bile helps break down the fats in your diet. If the flow of your bile changes, you may notice a change in your stool color.
• If bile moves too quickly through your intestines, which can happen with diarrhea, its color may not have a chance to change from green to brown as it processes food.
• If you are on a high-fat diet like the keto diet, your liver will make more bile to digest the fats. When this happens, your poop may come out with more green bile and take on a bright green color.
• If a surgeon removes your gallbladder, bile will flow directly from your liver to your small intestine. This can cause a temporary change in the color of your stool.

When to Seek Medical Attention

While occasional green poop is usually harmless, contact your physician if you experience:

• Severe abdominal pain or cramping
• Fever
• Bloody or jet-black poop
• Severe and persistent diarrhea
• Dehydration
• Weight loss

Dr. Kassim recommends looking at your stool regularly to understand your normal color and when there are changes. "Just take a peek in the toilet after you go, even when you're feeling fine," she says. "That will give you a baseline. If you notice a sudden or lasting change in color, regardless of the color, and it's not related to your diet, talk to your doctor."

Learn more about what your stool says about your health.