Green poop that lasts a full week usually comes down to one of three things: something you’re eating or drinking regularly, a medication or supplement you started recently, or your digestive system moving food through faster than normal. All shades of brown and even green are considered typical stool colors, so a week of green isn’t automatically a red flag. But when it persists this long, it’s worth understanding what’s behind it.
How Stool Gets Its Color
Your liver produces bile, a yellow-green digestive fluid that helps break down fats. As bile travels through your intestines, bacteria chemically transform it into the brown pigment you’re used to seeing. That conversion takes time. Normal gut transit, from eating to elimination, averages about 28 hours, with anything from 12 to 60 hours falling in the typical range.
When food moves through your system faster than usual, bile doesn’t fully break down, and the stool retains that original green color. This is the single most common mechanism behind green poop, regardless of the trigger. Anything that speeds up digestion, whether it’s a stomach bug, stress, a new medication, or a dietary change, can keep bile green all the way through.
Foods and Drinks That Turn Stool Green
If you’ve been eating the same green-heavy meals all week, your diet is the most likely explanation. Chlorophyll, the pigment that makes plants green, passes through your digestive tract and can directly tint your stool. The usual suspects include spinach, kale, broccoli, avocados, fresh herbs, and matcha. Even pistachios contain enough chlorophyll to shift stool color. Blueberries can also produce green shades, which surprises most people.
Artificial food dyes are another common cause. Brightly colored frosting, candy, sports drinks, or anything with concentrated dye can change stool color for days. If you ate a large amount of rainbow-colored candy or drank several green-tinted beverages over the course of a week, that alone could explain what you’re seeing. The color change is harmless and stops once you cut back on the trigger food.
Supplements and Medications
Iron supplements are one of the most reliable causes of dark green (sometimes nearly black) stool. This color change is actually considered a sign the supplement is being absorbed. If you started iron tablets around the same time the green appeared, that’s almost certainly the connection, and it will continue for as long as you take them.
Certain antibiotics can also tint stool yellow or green. They do this both by directly affecting bile chemistry and by disrupting the gut bacteria responsible for converting bile to its usual brown. If you recently finished or are currently on a course of antibiotics, expect the color to normalize within a few days to a week after your last dose.
Infections That Cause Green Stool
When a stomach bug speeds up digestion, bile passes through too quickly to change color. Several common infections cause this, including salmonella, E. coli, norovirus, rotavirus, and the parasite Giardia. The key difference between infection-related green stool and a dietary cause is that infections come with other symptoms. Salmonella typically brings diarrhea, stomach cramps, and fever. Norovirus causes stomach pain, diarrhea, and vomiting. Giardia tends to produce especially foul-smelling, greasy stools along with gas, bloating, and cramps.
If your green stool has been watery or loose for the full week and you’re also experiencing any combination of fever, vomiting, abdominal pain, blood or mucus in the stool, or signs of dehydration, an infection is more likely than a simple dietary cause. Most viral stomach bugs resolve on their own within a few days, so a full week of symptoms with no improvement makes bacterial or parasitic causes worth investigating.
Digestive Conditions Worth Considering
When green stool keeps returning over weeks or months (not just a single week), it can point to conditions that affect how your body processes bile. Bile acid malabsorption is one example: your small intestine fails to reabsorb bile acids properly, sending excess bile into the colon and causing chronic, often watery diarrhea with a greenish tint. This condition is associated with Crohn’s disease, celiac disease, irritable bowel syndrome, small intestinal bacterial overgrowth (SIBO), and chronic pancreatitis.
A single week of green stool without other ongoing digestive issues doesn’t strongly suggest any of these conditions. But if you’ve noticed a pattern of green or unusually loose stools recurring over several weeks, especially alongside persistent bloating, gas, or cramping, it’s worth bringing up with your doctor. These conditions are diagnosable and treatable, but they rarely announce themselves with color changes alone.
What to Do About a Week of Green Stool
Start by reviewing what’s changed in the past week or two. New green smoothie habit? Iron supplement? Antibiotics? A bout of food poisoning you thought had passed? Most of the time, one of these explains everything, and the fix is simply waiting it out or adjusting your diet.
If the green stool is solid, formed, and your only symptom, it’s almost certainly benign. Track what you’re eating for a few days and see if reducing green vegetables, matcha, or dyed foods makes a difference. The color should shift back to brown within one to two days of removing the trigger, since that’s roughly how long food takes to move through your system.
If the stool is consistently loose or watery, if you’re running a fever, or if you notice blood or mucus, those accompanying symptoms matter more than the color itself. Persistent diarrhea lasting a full week with no improvement, regardless of color, is worth a medical evaluation to rule out bacterial or parasitic infections that may need targeted treatment.