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Why does poop turn green and other colors?

Poop can turn green for a number of reasons, including eating many high chlorophyll plants, such as spinach or kale, taking an antibiotic course, or taking a bacterial infection. Although rarely a cause for concern, the poop color changes should be explored.

Poop is usually brown, but it may often turn orange, red, black, yellow or anything in between. Many of these variations in color do not suggest a medical condition but others may be a sign of something more severe.

This article addresses the color of the feces, what that means and when to speak to a doctor.

Fast facts on poop color

  • Certain foods and drinks can have significant effect on poop color
  • Poop can turn green due to diarrhea
  • Long-term changes to poop color should be examined by a doctor


A man going to toilet
Does green poop indicate illness? There are many reasons why stool can change color.

What is it that makes the poop green? Green stool in somebody’s diet is usually the result of a high amount of leafy, green vegetables. In fact, it is the plant’s chlorophyll that produces the green colour. Alternatively, after attending a birthday party, children may have green stool with which they eat chemically colored frosting.

Diet-based causes for green poop are by far the most popular, but there are others; people who don’t eat a lot of greens or coloring food should be careful, as green poop may have a more serious cause.

Bile pigment – the stool can be green in the stool because of bile pigment. If the food passes through the intestine too fast, the bile pigment can not break down sufficiently. One probable cause is diarrhea.

Antibiotics-An antibiotic course affects the types of bacteria found in the intestine. Since bacteria affect the poop’s usual color, a change in bacteria can also lead to a change in stool color, often to green.

Such medical procedures – for example, if a transplant of the bone marrow is refused, it can cause graft versus host disease. Diarrhea and green stubble are among the effects of this disease.

Parasites and bacteria – Certain parasites, including the Salmonella bacterium, Giardia (a water-based parasite), and norovirus may cause poop to turn green. These unexpected guests will cause the guts to function faster than usual, having an effect on the color of stools.

People who think their green stool isn’t the product of a diet rich in vegetables or coloring green food should speak to their doctor about that.

Colors of poop (graphics)
Image credit: Stephen Kelly, 2018

Factors of poop color

The normal stubble color should be a dark brown to a light. A red blood cell substance called bilirubin gets broken down and ends up in the intestines. Then, the bacteria break it down and turn it brown.

So, what does that mean when the poop unexpectedly changes color, and what are some of the potential causes?

Dietary changes may produce varying colors of stools; this is the most frequent cause. Eating beets, green vegetables (because of the high chlorophyll content), or liqueur can alter stool color significantly. Drinking Guinness or beverages containing heavy dye like Kool-Aid can have a similar effect.

However, there are more severe causes of non-brown stool color that should be treated immediately, if found.

Below is a short list of potential diseases that can affect stool colour:

  • Tears in the lining of the anus
  • Gallbladder disease
  • Celiac disease
  • Ulcerative colitis – a condition where the top layer of the large intestine lining is inflamed
  • Crohn’s disease – a condition where all of the large intestine can become inflamed
  • Tumors
  • Diverticular disease – a condition where pouches form in the intestine
  • Infections – bacteria and parasites can change stool color; for instance, Salmonella and Giardia can both lead to green stools
  • Cancers
  • Piles (hemorrhoids)
  • Bleeding in the gut

It’s hard to assign a particular color to each illness consistently. There are however some general features that can act as a reference.

  • Reddish stool – can be caused by bleeding in the lower gut or rectum.
  • Yellowish, greasy, smelly stool – can indicate an infection in the small intestine. It could also be a sign of excess fat in the stool due to a malabsorption disorder, celiac disease for instance.
  • White, light, or clay-colored – this can indicate a lack of bile in the body, possibly from a blocked bile duct. Certain medications can also cause this discoloration, such as bismuth subsalicylate (e.g. Pepto-Bismol) and other anti-diarrheal medication.
  • Black or dark brown – could indicate bleeding in the upper digestive tract, for instance, the stomach. Alternatively, it could be caused by iron supplements or bismuth subsalicylate.
  • Bright red – bleeding in the lower digestive tract (rectum, for instance) or, commonly, hemorrhoids. Alternatively, it may be due to red food coloring, cranberries, beets, tomato-based products, red gelatin, or drinks with red food coloring.
  • Green – eating large quantities of green dye, green vegetables; a course of antibiotics, or a bacterial infection.

It is best for people to see a doctor if any discoloration occurs, rather than trying to sort it out on their own.


T is important to know what to look for in relation to the more severe causes of discoloration of stools. This may include conditions like diverticulitis, Crohn’s disease, and cancer that normally presents with anus bleeding.

Important symptoms to look out for include:

  • Dark, tarry stools
  • Large amounts of blood passed from the rectum
  • Blood in the toilet bowl
  • Itchy anus
  • Swollen blood vessels in the rectum
  • Small tears in the skin of the anus
  • An urge to keep passing stools even when the bowel is empty
  • A small channel developing between the end of the bowel and the skin of the anus

Pay attention to any other signs associated with stool discoloration as well as any traces of blood in the urine, or general bleeding from the anus. May include lightheadedness, dizziness, nausea or vomiting, especially if the vomit also contains blood.

Inflammation of the gut can lead to rectal bleeding.
Inflammation of the gut can lead to rectal bleeding.

People should seek a doctor’s advice right away if any of those symptoms persist. Popular causes of bleeding at the rectum include:

  • Piles (hemorrhoids)
  • Tears in the lining of the anus
  • Anal fistula – a small channel that develops between the end of the bowel and the skin of the anus
  • Angiodysplasia – swollen blood vessels in the gut
  • Gastroenteritis – inflammation of the gut
  • Diverticular disease
  • Bowel cancer (colon or rectal cancer)

Less common causes of rectal bleeding include:


Before flushing it away it is worth a brief look at the stool. Stool is an ideal predictor of how the digestive system is working properly. If there are any diseases that occur in the body like the ones listed above, stool that offer a clue.

According to the Bristol Stool Map our stool is distinguished by seven shapes and formations. Each denotes something concerning the diet or body of a person.

The Bristol Stool Chart

  • Type 1: Separate, hard lumps, like nuts (that are often hard to pass)
  • Type 2: Sausage-shaped but lumpy
  • Type 3: Sausage-shaped but with cracks on the surface
  • Type 4: Sausage- or snake-like, smooth and soft
  • Type 5: Soft blobs with clear-cut edges (easy to pass)
  • Type 6: Fluffy pieces with ragged edges, mushy
  • Type 7: Watery, no solid pieces (entirely liquid)

Form 3 or 4 is the perfect stool as a general rule, since it is easy to move without being too watery. Form 1 or 2 means probable constipation of a individual. Form 5, 6, or 7 indicates a person is likely diarrhea.

This chart helps doctors recognize problems, and track the time it takes to move through the digestive system for food. The shape and form of the stool will also help the doctors make a correct diagnosis.


To control stool color the most important thing to do is eat healthily. The best color for stools is light to dark brown, as discussed earlier. Some people who have a high amount of greens in their diet can pass poop which also has a green colour.

Having a green poop is generally not a cause of concern. However, keeping an eye on both the color and the texture of your stool is important to people. Anyone worried about their stool color should discuss this with their doctor.

Chukwuebuka Martins

Chukwuebuka Martins is a writer, researcher, and health enthusiast who specializes in human physiology. He takes great pleasure in penning informative articles on many aspects of physical wellness, which he then thoroughly enjoys sharing to the general public.

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