Stool Color, Changes in Color, Texture, and Form

  • Medical Author:
    Benjamin Wedro, MD, FACEP, FAAEM

    Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

  • Medical Editor: Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)
    Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)

    Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)

    Dr. Anand received MBBS degree from Medical College Amritsar, University of Punjab. He completed his Internal Medicine residency at the Postgraduate Institute of medical Education and Research, Chandigarh, India. He was trained in the field of Gastroenterology and obtained the DPhil degree. Dr. Anand is board-certified in Internal Medicine and Gastroenterology.

Stool color changes can be caused by a number of underlying conditions.

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:
  • Changes in stool color may be due to diarrhea; bleeding in the intestine; diseases of the intestines, liver, or pancreas; 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 colored stool may be a sign of bleeding in the GI 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 (GI) 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.

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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.

Stool, feces, or poop is the waste product of digestion.

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 samples are taken to test for causes of stool color changes.

What is the color of normal stool?

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 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 stool is dilute or there is a reduction in the amount of bilirubin that is 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.

woman with abdominal pain
Eating beets can be a harmless cause of stool color changes.

What are the causes of stool color, texture, and form changes?

In most cases, stool color changes are not symptoms of disease. Changes in stool color may be due to:

  • Diarrhea may cause green or yellow stools.
  • Some foods (beets, Jell-O, 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

Green stools

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 bile is chemically changed by bacteria in the intestine 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. They also can be caused by a diet rich in green vegetables, especially spinach. Iron supplements also may be a cause, though iron often turns stool black.

Stool color changes to yellow can signal undigested fats.

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 is due to the undigested fat.

Stool color changes to bright red could be a sign of hemorrhoids.

Bright red stools

  • The most common cause of bright red stool in adults is bleeding from hemorrhoids.
  • In infants, the most common cause is an anal fissure or tear in the tissue surrounding the anus.
  • Other causes for bright red blood in the stool may be more serious such as:
  • Infections of the intestines
  • Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
  • Diverticular bleeding
  • Tumors
  • Arteriovenous malformations (abnormal communications between arteries and veins in the wall of the intestine that rupture).
  • Brisk bleeding from the an ulcer in the esophagus, stomach, or duodenum also may cause stools to be red instead of black if there has not been enough time for the red blood cells to be digested.
  • Red food coloring and beets can also give a reddish hue to the stool.
Black stool and tarry stool can be a worrisome sign of GI bleeding.

Black tarry stools

Black stools are a worrisome symptom because it may be due to a large amount of bleeding into the GI tract, 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 tarry (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.

Stool color changes to a pale or clay color could signal a bile blockage.

Light-colored white or clay-colored stools

White-or clay colored stool are often seen with diseases of the liver or bile ducts. It also 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 stools

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 situation.

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.

Prescription drug labels often include stool color changes as a warning.

Mucous in the stool

Mucous in the stool may be normal, and it may cover segments of formed feces. However, it also can occur in people with inflammatory bowel disease or cancer. Mucous that is also associated with blood and/or abdominal pain should not be ignored and requires medical attention. People with irritable bowel syndrome (IBS) also can have mucous in the stool.

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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Floating stool is caused by excess gasses.

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 stool that floats, but as an isolated symptom, no action needs to be taken, and often it resolves spontaneously. 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 with lactose intolerance, celiac disease, cystic fibrosis, and short bowel syndrome.

woman with abdominal pain
Stool color changes and changes in size may happen occasionally.

Changes in the size and shape of stool

Each person has their own size, shape and consistency of stool. It is the change in stool pattern that matters more than the absolute size and shape of 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 a 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 a third stool it will be loosest of all. 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.

Call your health-care professional if you have any troublesome stool color changes.

What kind of doctor treats 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 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 health-care professional 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.

Stool color chart

Stool Color Changes
Potential CauseCommentSub-Header
BlackGI bleedingThis is an emergency
BlackIron, bismuthCannot presume this to be the reason for the stool color
MaroonGI bleedingThis is an emergency
RedHemorrhoidsOnly one of the potential causes. Do not ignore
RedInflammatory bowel diseaseConsult health-care professional
RedInfection, diverticular bleedConsult health-care professional
RedTumor, rapid upper GI bleedConsult health-care professional
GreenMay be normalConsult health-care professional
GreenDiet high in green vegetablesConsult health-care professional
GreenAssociated with diarrheaConsult health-care professional
BrownNormal colorConsult health-care professional
YellowDiseases of the pancreasMalabsorption
YellowCeliac disease, cystic fibrosisConsult health-care professional
YellowGiardia infectionConsult health-care professional
Clay, pale yellow or whiteLiver or biliary diseaseLack of bile in the stool

Reviewed on 6/28/2017
References
REFERENCE:

Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

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