Green poop is usually bile that did not have time to turn brown - because your gut moved fast for a few days - or food that arrived green: leafy vegetables, food colouring, or iron supplements.
MedlinePlus confirms bile salts give stool its brown colour and that fast transit causes diarrhoea. Alone and brief, it needs nothing. Pymander is a free AI doctor, 24/7 by text, and can help you read the picture.
What to do
Common questions
Why is my poop green?
The colour of your stool is mostly a bile story. The liver releases bile into the gut to digest fats, and MedlinePlus explains that bile salts give stool its normal brown colour - bile starts out greenish and turns brown as it travels and gut bacteria work on it. Anything that speeds the journey short-circuits the browning: MedlinePlus notes diarrhoea happens when stool passes through the large intestine too quickly, and a fast gut is the most common reason healthy people see green. A stomach bug, a laxative, or an antibiotic can all speed transit for a few days. The even more boring cause is what you ate: a big spinach or kale-heavy few days, green or blue food colouring in drinks and sweets, and iron supplements all tint the result directly. Green poop alone, in an otherwise well person, needs no action at all. The colours that do deserve attention: pale or clay-coloured stools (which can mean bile is not reaching the gut - MedlinePlus links this to liver or gallbladder problems, especially with yellowing skin), black tarry stools, or visible red blood, and green diarrhoea that runs past a few days or comes with fever, weight loss, or severe pain. Those get a GP visit; the rest gets a shrug and a normal week of eating. Pymander is a free AI doctor, 24/7 by text, that can help you read the whole picture.