Stool color changes can be caused by a number of underlying conditions.Source: iStock
Stool color, texture, and form changes facts
- The normal stool (poop, feces) usually is light to dark brown.
- Although changes in stool color or texture may be normal, most changes should be evaluated.
- The symptoms associated with stool color changes, if any, are the symptoms of the underlying cause of the change, for example, foods, drinks, or illnesses such as:
- Stool that is an unusual color may be due to diarrhea; bleeding in the intestine; intestine, pancreas, or liver diseases; and medications
- Green stool or poop is a common stool color change. It may be due to bile pigment in the stool because diarrhea moves food too quickly thorough the intestine so the intestinal chemicals and bacteria can’t break down the bile pigment to its normal brown color, or the green color may be due to certain foods like green, leafy vegetables or green food coloring.
- Red or black poop may be a sign of bleeding in the digestive tract (from the esophagus, stomach, small intestine, or colon) and should not be ignored.
- When stool color changes, what tests need to be done depends upon what cause is suspected for the stool color change. For example, gastrointestinal tract endoscopy may be required to evaluate red or black stools if bleeding is suspected.
- The treatment for stool color changes is the treatment of the underlying cause.
Rectal Bleeding (Blood in Stool, Hematochezia)
Causes of Blood in Stool
Blood in the stool can be bright red, maroon in color, black and tarry, or occult (not visible to the naked eye). Causes of blood in stool range from harmless, annoying conditions of the gastrointestinal tract such as hemorrhoids to serious conditions such as cancer.
The underlying cause of the change in stool color, texture, or form is responsible for any symptoms.Source: Getty Images
What are symptoms of stool color changes?
Changes in stool color alone do not cause symptoms. The underlying cause of the change in stool color, texture, or form is responsible for any symptoms.
What does it mean when your stool color changes in color, texture, or form?
Bowel movements are usually light to dark brown in color, and there is moderate variation among individuals with respect to stool color, quantity, and form. When these changes in stool do occur, it can mean that there may be an illness affecting the gastrointestinal (GI) tract or the entire body.
Stool color chart
|Black||GI bleeding||This is an emergency|
|Black||Iron, bismuth||Cannot presume this to be the reason for the stool color|
|Maroon||Gastrointestinal bleeding||This is an emergency|
|Red||Hemorrhoids||Only one of the potential causes. Do not ignore|
|Red||Inflammatory bowel disease||Consult a health care professional|
|Red||Infection, diverticular bleed||Consult a health care professional|
|Red||Tumor, rapid upper GI bleed||Consult a health care professional|
|Green||May be normal||Consult a health care professional|
|Green||Diet high in green vegetables||Consult a health care professional|
|Green||Associated with diarrhea||Consult a health care professional|
|Brown||Normal color||Consult a health care professional|
|Yellow||Diseases of the pancreas||Malabsorption|
|Yellow||Celiac disease, cystic fibrosis||Consult a health care professional|
|Yellow||Giardia infection||Consult a health care professional|
|Clay, pale yellow or white||Liver or biliary disease||Lack of bile in the stool|
Changes in the chemical structure of the bilirubin can cause stool to turn green or yellow.Source: Getty Images
What is the color of normal stool?
The stool (feces, poop) color is most commonly brown. When stool color changes, a person, parent, or caregiver often becomes concerned.
- The presence of the bilirubin in the bile (a breakdown product of the hemoglobin in red blood cells that are normally destroyed after a useful life of several weeks) is generally responsible for stool color.
- Bilirubin concentration can vary the color of the stool from light yellow to almost black.
- Changes in the chemical structure of the bilirubin can cause stool to turn green or yellow.
- Yellow stool also may occur if the stool is dilute or a reduction in the amount of bilirubin produced by the liver.
- Bacteria and digestive enzymes in the intestine can act on the bilirubin and change its color.
Most stool-to-stool changes in color have little meaning. However, some changes, particularly if the changes are consistent over time and not present in only one stool may mean something needs to be investigated.
Changes in stool color may be due to diarrhea that may cause yellow-green stools.Source: iStock
What are the causes of stool color, texture, and form changes?
In most cases, poop color changes are not symptoms of the disease. Changes in stool color may be due to:
- Diarrhea may cause yellow-green stools.
- Some foods (beets, Jell-O, Kool-Aid, licorice, green leafy vegetables)
- A few over-the-counter (OTC) and prescription medications
- Diseases affecting the liver, pancreas, and intestines
- Bleeding from the intestinal tract
If stool passes through the intestine too quickly, there might not be enough time for bile to be digested and broken down to provide the normal brownish stool color. Normally, bacteria in the intestine chemically change bile to a greenish-brown color. It takes time for the bile to be fully changed in the intestine and become brown again, and if the transit time is short, for example, when a person has diarrhea, the stool remains green-colored.
Green stools may be a normal variant. A diet rich in green vegetables, especially spinach, or Iron supplements also may cause green poop, though iron often turns stool black.
It can be due to the intestine’s inability to digest and absorb fat because of diseases of the intestinal lining (such as celiac disease and cystic fibrosis).Source: iStock
Yellow, greasy, and foul smelling stool
There are a variety of reasons why stool will be yellow, greasy, and foul-smelling. It can be due to the intestine’s inability to digest and absorb fat because of diseases of the intestinal lining (such as in celiac disease and cystic fibrosis) because the pancreas is unable to manufacture adequate digestive enzymes (such as with chronic pancreatitis or pancreatic cancer that blocks the pancreatic duct), or there is not enough bile being delivered to the intestine (such as in cancer of the liver or bile ducts that are blocked). The yellowness, greasiness, and foul smell are due to the undigested fat.
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Black stools are a worrisome symptom because it may be due to a large amount of bleeding into the digestive system, most often from the upper GI tract including the esophagus, stomach, and duodenum.Source: iStock
Black tarry stools
Black stools are a worrisome symptom because it may be due to a large amount of bleeding into the digestive system, most often from the upper GI tract including the esophagus, stomach, and duodenum. Red blood cells are broken down by digestive enzymes in the intestine and turn the stool black. These stools tend to be tar-like (sticky) and foul-smelling. This can be a medical emergency; black tarry stools should not be ignored.
Blood from nosebleeds or from dental procedures or mouth injuries can be swallowed and may be the cause of black stool, but the amount of bleeding usually is not substantial enough to do this.
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Light-colored or clay-colored stools are often seen with diseases of the liver or bile ducts.Source: Getty Images
Clay-colored or white stools (pale stools)
Light-colored or clay-colored stools are often seen with diseases of the liver or bile ducts. The pale stool may be caused by pancreatic cancer that blocks the bile ducts. Lack of bile causes stool to lose its brown color and leaves it appearing pale.
Maroon colored stools are often due to bleeding in the GI tract. The source of bleeding for red stools is the upper GI tract (esophagus, stomach, duodenum), while the colon is the source for bright red blood. Maroon stools, which is caused by partial digestion of the blood in the intestine often arises from the small intestine (jejunum, ileum) and proximal colon, but the color also depends in part on how rapidly the blood travels through the intestines. The faster the stool moves through the GI tract, the brighter red the color. This can be an emergency.
In children with intussusception, where one portion or the intestine telescopes into another part, causing a temporary obstruction, stools may be described as currant jelly in color and consistency.
Mucus in the stool may be normal, and it may cover segments of formed feces.Source: Getty Images
Drugs that change stool color
The most common medications that change the color of stool are the drugs that turn the stool black and include iron and bismuth (contained in Pepto-Bismol and Kaopectate). Nevertheless, a large number of other drugs have been associated with changes in the color of stool to black or other colors. Practically, the importance of this fact is that the any new drugs or dietary supplements need to be considered as the cause of any change in stool color.
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Most stool floats because it contains an excessive amount of gas.Source: iStock
Stool that floats
Most stool floats because it contains an excessive amount of gas. By itself, it is normal and has little meaning. Changes in diet can lead to the stool that floats, but as an isolated symptom, no action needs to be taken, and often it resolves spontaneously. The stool does not float because of an increased amount of fat. (Fat in stool causes oil droplets in the toilet bowl.)
Any condition that causes increased amounts of gas to form in the intestines theoretically may lead to floating stool, especially in conditions where there is malabsorption of nutrients such as lactose intolerance, celiac disease, cystic fibrosis, and short bowel syndrome.
People with irritable bowel syndrome (IBS) may develop thinner stools.Source: Getty Images
Changes in the size and shape of stool
People have their own size, shape, and stool consistency. It is the change in stool pattern that matters more than the absolute size and shape of the stool. Narrow stool, sometimes called pencil-thin, may occur occasionally and is of no concern. People with irritable bowel syndrome (IBS) may develop thinner stools.
Nevertheless, a person with “normal” stools that has a new change in the diameter, length, width (caliber) of the bowel movement should consult his/her health care professional. This may be a sign of a narrowed or scarred colon, perhaps due to a tumor, but the health care professional may want further information about accompanying symptoms or tests.
It is not unusual to have two or even three stools in the morning. The first stool will usually have a more solid form because it has been in the colon (where water is absorbed) the longest. The second stool will be looser, and if there is the third stool, it will the loosest. Another change in stool form that often requires evaluation is the development of looser or firmer than normal stools. At one end of the spectrum is constipation and at the other end is diarrhea, but even if the change does not reach these levels, consistent, milder changes in either direction need to be evaluated.
Depending upon the cause of the stool color change, certain specialists may need to be involved.Source: Istock
Which type of doctors treat stool color changes?
Most often, people will contact their primary care health care professional with questions about the color of their stool. These include health care professionals who care for infants and children. Depending upon the cause of the stool color change, certain specialists may need to be involved. For example, for red or black stool due to bleeding, a gastroenterologist may be needed to perform an endoscopy, to look for a bleeding source in the stomach or intestine. Gastroenterologists are the specialist that helps manage other diseases of the intestinal tract, including Crohn’s disease, pancreatitis, and celiac disease, that can cause color changes because of poor absorption of nutrients from the diet.
How is the cause of stool color changes diagnosed?
In most cases, a diagnosis, if any, cannot be made by stool color alone.
The patient and the doctor need to consider other symptoms, past medical history, dietary changes, and medications to help decide what has caused the stool to change color. Physical examination will be important to help decide the significance of the stool color.
Stool may be tested to look for blood, fat, or infection. Blood tests may be necessary depending upon the clinical situation. Depending on the change in color, it may be necessary to evaluate the pancreas, liver or GI tract.
When should I contact my doctor about stool color or texture changes?
Aside from black, red, or maroon stools that may mean bleeding is a possibility, and require urgent assessment and treatment, most color changes are not an emergency. The significance is determined based on other symptoms that might be present.
Women who are pregnant often note changes in their bowel pattern. Stool can turn black because of iron and vitamin supplements. Iron can also turn stool greenish. As the uterus enlarges and increases pressure within the pelvis, constipation may occur and hemorrhoids can develop and cause blood in the stool.
If there is no underlying problem, stool color changes are often due to changes in the diet and will resolve in a couple of days. If this is not the case and changes persist, it is appropriate to contact your health care professional and seek medical attention.
Contact your doctor if you have stool color changes and have associated symptoms such as vomiting, diarrhea, fever, or abdominal pain.
It is important to remember that every person is different and changes in bowel habit be it color, size, frequency, or consistency (hard or soft) may be normal for one person or a sign of a potential problem for another.
Medically Reviewed on 7/26/2021
Rakel, R.E., and D. Rakel. Textbook of Family Medicine, 9th Edition. Saunders, 2015.