Why Is My Poop Green? Stool Colors Explained - Medical News Today

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Human Biology

Why does poop turn green and other colors?

Medically reviewed by Qin Rao, MD — Written by Gareth Strachan — Updated on April 22, 2025

Causes
Changes
Symptoms
Consistency
FAQ
Summary

Poop can turn green for many reasons, such as a diet rich in high chlorophyll plants. Other possible causes include antibiotic use and bacterial infections.

Poop is generally brown, but, at times, it can turn green, red, black, yellow, or any color in between. Many of these color changes do not signal a medical condition, but some can be signs of something more serious.

This article discusses poop color, what it can mean, and when to speak with a doctor.

Causes of green poop

Why does poop turn green and other colors infographic — Infographic by Stephen Kelly

According to Guts UK, green stool is usually the result of eating a large quantity of leafy, green vegetables. This is because chlorophyll in the plants produces a green color.

Alternatively, people may have green stool after eating artificially colored foods, such as frosting from a cake.

Certain foods in a person’s diet are the most common causes of green poop. However, people who do not eat a lot of greens or food coloring should be aware that green poop can have a more serious cause.

Other possible causes include:

Bile pigment: Green stool can be due to bile acid malabsorption. If food moves too quickly through the intestine, bile pigment cannot break down sufficiently and stays in the stool.
Antibiotics: Antibiotics can change the types of bacteria present in the gut. Because bacteria influence the color of poop, a change in bacteria may mean a change in stool color.
Certain medical procedures: For example, a person whose body rejects a bone marrow transplant may develop graft-versus-host disease, which may cause changes to the stool.
Parasites and bacteria: Certain pathogens can cause poop to turn green, such as the Salmonella bacterium, the water-based parasite Giardia, and norovirus. They can cause the guts to move food more quickly, affecting stool color.

People who think their green stool is not the result of a diet rich in vegetables or green food coloring should discuss it with a doctor.

What can change poop color?

Stool is usually light to dark brown. A substance from red blood cells called bilirubin ends up in the intestines. Bacteria break it down and it turns stool brown.

Changes in diet can produce varying stool colors. For example, eating beetroot, high chlorophyll green vegetables, or licorice can significantly change stool color. Drinking dark stouts or drinks that contain dyes, such as flavored drink mixes, can have a similar effect.

In infants, foods may cause color changes, including the following:

green stool — spinach, breast milk, formula
red stool — beetroot, tomato soup, cranberry juice, other red drinks
black stool — licorice, grape juice

However, some causes of non-brown stool are more serious, and it is important to talk with a doctor about these issues immediately. Health conditions that may change the color of stool include:

anal fissures, or tears in the lining of the anus
gallbladder disease
celiac disease
ulcerative colitis, a condition causing colon inflammation
Crohn’s disease, a condition in which all layers of the small and large intestines can become inflamed
cancerous tumors in the gastrointestinal (GI) tract
cancers of other digestive organs
diverticular disease, a condition in which pouches form in the large intestine
bacterial or parasitic infections, such as Salmonella or Giardia
hemorrhoids
bleeding in the gut

What each color indicates

It is difficult to consistently relate a precise color to each condition. However, here are some possible connections between colors and conditions:

Reddish or maroon: This may be a sign of bleeding somewhere in the GI tract.
Yellowish, greasy, smelly: This 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 such as celiac disease.
White, light, or clay-colored: This can indicate a lack of bile in the body, possibly from a blocked bile duct.
Black or dark brown: This can be a sign of bleeding in the upper GI tract, such as the stomach. Alternatively, it could be the result of iron supplements or bismuth subsalicylate.
Bright red: Bleeding in the lower digestive tract, such as the rectum or anus, may cause bright red stool. Hemorrhoids and anal fissures may also cause bright red stool. Alternatively, red stool may be due to dietary factors, such as beetroot.
Green: Large quantities of green dye or green vegetables, antibiotics, or a GI tract infection may cause green stool.

If any discoloration persists, it is important that a person contacts a doctor instead of trying to work it out on their own.

Symptoms

The more serious possible causes of stool discoloration include conditions such as diverticulitis, Crohn’s disease, ulcerative colitis, and cancer, which can manifest with bleeding from the lower GI tract.

Important symptoms to look out for include:

dark, tarry stools
red or maroon stools
large amounts of blood from the rectum
blood in the toilet bowl
an 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

As well as any traces of blood in the stool or bleeding from the anus, people should pay attention to any other symptoms that occur with stool discoloration. These may include nausea, vomiting blood, or a feeling of fullness without eating.

People should seek the advice of a doctor immediately if any of these symptoms persist.

Potential causes of rectal bleeding include:

piles, also known as hemorrhoids
inflammatory bowel disease
anal fissures
anal fistula
rectal or anal cancer

Stool consistency

It is worth having a quick look at the stool before flushing it away. Stool is a very good indicator of whether the digestive system is working correctly. It may provide a clue to illnesses such as those mentioned above.

According to the Bristol stool chart, there are seven shapes and consistencies of human stool. Each one suggests something about a person’s diet or body.

The Bristol stool chart

Type 1: This type involves separate, hard lumps, similar to nuts, which are often hard to pass.
Type 2: Stool is sausage-shaped but lumpy.
Type 3: Stool is sausage-shaped but with cracks on the surface.
Type 4: This type is sausage- or snake-like, smooth and soft.
Type 5: Stool may be soft blobs with clear-cut edges that are easy to pass.
Type 6: This type involves fluffy, mushy pieces with ragged edges.
Type 7: Stool is watery with no solid pieces — entirely liquid.

As a general rule, type 3 or 4 is the ideal stool, as it is easy to pass but not too watery. Type 1 or 2 means that a person may be constipated. Type 5, 6, or 7 indicates a person may have diarrhea.

This chart helps doctors identify problems and correlate the time food takes to pass through the digestive system. The shape and form of stool may also help doctors make a diagnosis.

»Learn more:The Bristol Stool Form Scale

Frequently asked questions

Is it OK to have green poop?

There are many reasons why poop may turn green, including illness or changes in diet. If any discoloration persists, it is important that a person contacts a doctor instead of trying to work it out on their own.

What is green poop a symptom of?

Green poop can be a symptom of changes in diet, taking antibiotics, having certain illnesses or parasites, or bile pigment.

When should someone be concerned about green poop?

Green stool usually happens as a result of eating certain foods, such as leafy green vegetables.If a person has not consumed a lot of green vegetables or other green foods, green stool could be due to an underlying health condition. It is best to contact a doctor for advice if they consistently or frequently have green stool.

Green stool usually happens as a result of eating certain foods, such as leafy green vegetables.

If a person has not consumed a lot of green vegetables or other green foods, green stool could be due to an underlying health condition. It is best to contact a doctor for advice if they consistently or frequently have green stool.

Is green poop an infection?

A bacterial infection in the GI tract may cause green stool. However, it may also be due to consuming green foods or antibiotics.

Summary

The most important thing to do to regulate stool color is to eat a nutritious, balanced diet. The ideal stool color is light to dark brown. Some people who eat large quantities of green foods may pass green poop.

Having green poop is not usually a cause for concern. However, it is important to keep an eye on both the color and the texture of stools. Anyone with concerns about the color of their stool should discuss them with a doctor.

GastroIntestinal / Gastroenterology
Nutrition / Diet

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Avoiding constipation: Bristol Stool Chart. (2022).https://publicdocuments.sth.nhs.uk/pil3883.pdf
Poo-torial. (n.d.).https://gutscharity.org.uk/advice-and-information/poo-torial/
Sabry AO, et al. (2023). Rectal bleeding.https://www.ncbi.nlm.nih.gov/books/NBK563143/

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Medically reviewed by Qin Rao, MD — Written by Gareth Strachan — Updated on April 22, 2025

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