Stool Color Changes

Reviewed on 10/18/2022

Stool Color Changes Facts

Stool color changes, depending on the color, can be harmless or an indication of a health problem, minor or serious.
Stool color changes, depending on the color, can be harmless or an indication of a health problem, minor or serious.
  • Normal stool color is brown. This is due to the presence of bile in the stool. Normal stool color can range from light yellow to brown to almost black.
  • If stool is red, maroon, black, clay-colored, pale, yellow, or green this may signify a problem.
  • Some causes of stool color changes include
  • Symptoms of stool color changes are usually related to the underlying cause and often there are no accompanying symptoms. When there are, they may include
  • Treatment for changes in stool color depends upon on the cause and can vary widely.
  • If stool color changes only happen once or twice (are transient) they are less of a concern than those that are persistent. Contact your doctor if the stool color changes are persistent.

What Causes Changes in Stool Color, Form, or Texture?

If your stool is black, the cause might be an iron supplement or over-the-counter medicine you took because your stomach felt bad.

Stool color can change for a variety of reasons. The change may reflect substances that are added to stool or changes to substances normally present in the stool. Some stool color changes may suggest an underlying medical condition, and others may be due to the ingestion of certain foods or medications.

Black Stools (Not Sticky, No Odor)

Causes of black stool include iron pills or bismuth-containing medications (such as bismuth subsalicylate or Pepto-Bismol). If the stool color is dark because of any of these medications, it is typically not sticky in texture and is not foul-smelling.

Black Tarry, Sticky Stools

Bleeding in the stomach (from gastritis or an ulcer) or the intestines can change the color of the stool. If bleeding occurs in the stomach or the upper part of the small intestine, the stool may turn black and sticky, and be described medically as black, tarry stool (melena). Generally, the black, tarry stool also is foul-smelling. This change in color and consistency occurs because of chemical reactions to blood within the intestine that are caused by digestive enzymes within the intestines.

Maroon or Red Stools

If the bleeding originates from lower parts of the intestines or the colon, blood may not come into prolonged contact with digestive enzymes because of the short distance from the site of bleeding to the rectum. Moreover, large amounts of blood within the intestines speed up the transit of stool so that there is less time for the changes to take place. The stool in this type of bleeding may be dark red or maroon in color. Beets, other red vegetables, cranberries, and red food dyes also can turn the stool color red or maroon.

Gray or Clay-Colored Stool

The stool can be gray or clay-colored if it contains little or no bile. The pale color may signify a condition (biliary obstruction) where the flow of bile to the intestine is obstructed, such as obstruction of the bile duct from a tumor or gallstone in the duct or nearby pancreas. The change of stool color to gray or clay typically occurs gradually as these medical conditions progress relatively slowly and stool becomes pale over time.

Yellow Stool

Stool that is yellow may suggest the presence of undigested fat in the stool.

This can occur as a result of diseases of the pancreas that reduce delivery of digestive enzymes to the intestines (pancreatic insufficiency), such as:

  • cystic fibrosis,
  • chronic pancreatitis (long-standing inflammation and destruction of the pancreas usually due to alcohol abuse), or
  • obstruction of the pancreatic duct that carries the enzymes to the intestines (most commonly due to pancreatic cancer).

Celiac disease: Another condition that possibly may cause yellow and greasy stool is celiac disease (a malabsorption syndrome).

The digestive enzymes released from the pancreas and into the intestines are necessary to help digest fat and other components of food (proteins, carbohydrates) in the intestines so that they can be absorbed into the body. If the pancreas is not delivering enzymes into the intestines, then components of food, especially the fat, can remain undigested and unabsorbed. The stool containing the undigested fat may appear yellowish in color, greasy, and also may smell foul.

Ingestion of very high-fat foods also can cause yellow, soft, and foul-smelling stools.

Weight loss medications such as orlistat (Xenical, Alli) work by limiting the amount of fat absorbed by the intestines. This can lead to bulky, yellow, and greasy stools.

Green Stool

When stool passes through the intestines rapidly (diarrhea), there may be little time for bilirubin to undergo its usual chemical changes, and stool can appear green in appearance due to rapid transit.

Eating excessive amounts of green foods, foods with green or purple dyes, and vegetables also can cause stool color to turn more green than normal.

What are the symptoms associated with stool color changes?

The symptoms associated with changes in the color of stool generally correspond to the underlying cause. In many instances, there may not be any symptoms associated with changes in stool color.

Bleeding from the gastrointestinal tract (esophagus, stomach, small intestine, large intestine) leading to red, maroon, or black tarry stools may at times be without any symptoms at all. Other times, these changes may have accompanying symptoms of:

  1. abdominal pain due to the underlying cause of the bleeding, for example, an ulcer;
  2. nausea, vomiting of blood, diarrhea, and cramping due to the presence of blood in the stomach and/or intestines; and
  3. weakness, lightheadedness, and dizziness, due to the loss of blood from the body.

Persistently gray or clay-colored stools suggest some type of obstruction to the flow of bile. Obstruction caused by gallstones usually is associated with pain on the right side of the abdomen. However, cancer of the bile duct or cancer of the head of pancreas, which also can cause obstruction to the flow of bile by pressing on the bile duct, may not be associated with abdominal pain unless the tumor is large. The obstruction to the flow of bile causes backup of bile into the blood resulting in yellowness of skin and eyes (jaundice).

Yellow stool as a result of undigested fat also may occur with no symptoms. If present, the most common symptom associated with yellow stool will be abdominal pain as a result of chronic pancreatitis, tumor of the pancreas, or obstruction of the pancreatic duct. Undigested fat can also produce flatulence (gas) and loose, foul smelling stools.

Stool color chart and what does it mean

The color of your stool depends on a couple of things: your diet and how much bile is in it. Almost any shade of brown, or even green, is considered OK.

Stool Color Changes Color Chart
Color Potential cause What to do
Maroon Gastrointestinal (GI) bleeding This is an emergency. Go to an emergency department.
Red — bright red blood Hemorrhoids, anal fissure Only two of the potential causes. Do not ignore it. Make an appointment with a doctor.
Red — dark red/maroon, sometimes with clots or mucus Inflammatory bowel disease (Crohn's disease, ulcerative colitis), infection, diverticular bleed, tumor, rapid upper GI bleed Consult doctor.
Green May be normal. A diet high in green vegetables is associated with diarrhea. Consult doctor.
Brown Normal color. Consult doctor.
Yellow Diseases of the pancreas, malabsorption, celiac disease, cystic fibrosis, Giardia infection Consult doctor.
Clay, pale yellow, or white Liver or biliary disease, lack of bile in the stool Consult doctor.
Black GI bleeding This is an emergency. Go to an emergency department.
Black Iron, bismuth Cannot presume this to be the reason for stool color. Consult a healthcare professional.

What kind of doctor treats stool color changes?

The evaluation of conditions such as intestinal bleeding or diseases of the pancreas, gallbladder, or liver, may warrant careful evaluation by an internist, a primary care provider (PCP) such as a family practitioner or pediatrician, internal medicine physician, general surgeon, or a gastroenterologist (a physician who specializes in diseases of the digestive tract).

When should I seek medical care for stool color changes?

A person should notify their doctor when there is a persistent change in the color of their stool.

Persistent black, tarry stools or red, bloody stools signify intestinal bleeding and need to be evaluated by a health-care professional promptly. Individuals should either notify their primary care doctor or visit an urgent care center or an emergency room.

Gray or clay-colored stool and yellow stool also may signify diseases of the pancreas, gallbladder, or the liver. The evaluation of these conditions may warrant careful evaluation by an internist, primary care physician, or a gastroenterologist (a physician specialized in disease of the stomach and the intestines).

How are the causes of stool color changes diagnosed?

The evaluation of changes in stool color typically begins with a thorough physical examination and personal medical history. The doctor may ask about intake of alcohol, smoking, and other habits. Family history of any cancers, particularly of the liver or pancreas, or bleeding problems may be helpful. A review of medications that may affect the color of stool, including over-the-counter (OTC) medications, also is important. Any changes in bowel habits (constipation, diarrhea, and change in frequency) or any pertinent symptoms (pain with or without eating, nausea, vomiting, weight loss, etc.) can provide clues in evaluating the underlying causes of changes in stool color.

Diagnostic testing to find the cause of changes in stool color typically start with blood tests including complete blood count (CBC),blood chemistries, liver enzymes (comprehensive metabolic panel or CMP or SMA 19), and blood clotting assays (tests of coagulation). These tests can help diagnose anemia, liver disease, gallbladder disease, or other underlying conditions that may be responsible for the changes in stool color. Pancreatic enzymes (amylase and lipase) also can be measured to determine if pancreatic disease may be present. Specific blood work for celiac disease, liver disease, and cystic fibrosis also may be evaluated if determined to be appropriate by your doctor.

If bleeding from the stomach or intestines is suspected but the stool is not visibly black, red, or maroon, then occult stool blood testing (small amount of blood that does not cause the color of stool to change much) can be done. This tests the stool directly for blood with a dye (fecal occult blood test or FOBT). Occult stool blood testing relies on a chemical reaction between a solution (called guaiac) and hemoglobin in a sample of stool. In the presence of hemoglobin, the drop of solution will turn the stool sample (smeared onto a special paper which reacts chemically with the solution) blue. This test is part of the recommendation for screening for colon cancer, although in clinical practice it is often used to determine if any bleeding is occurring in the gastrointestinal system. In addition to the test using guaiac, there is an immunological test for blood in the stool that uses an antibody to hemoglobin to detect the blood.

Methods to evaluate a change in the color of stool are upper gastrointestinal endoscopy (esophago-gastro-duodenoscopy or EGD), and colonoscopy. These tests are done by gastroenterologists to look inside the esophagus and stomach (EGD) and the colon (colonoscopy) with a video camera to detect the source of the bleeding or other abnormality that may explain the change in stool color. If necessary, biopsies can be taken with these techniques. Colonoscopy with biopsy also may aid in diagnosing conditions such as celiac disease.

More advanced endoscopic testing to look for obstruction of the biliary or pancreatic ducts is done by endoscopic retrograde cholangio-pancreatography or ERCP. This test is performed like an EGD except that during the test dye is injected into the biliary and pancreatic ducts to look with X-rays for obstruction of the ducts.

Other imaging studies sometimes are necessary in order to find the cause of the change in stool color. Computerized tomography (CT scan) is ordered frequently by physicians if the change in stool color is believed to be related to underlying cancer, pancreatic disease, or obstructive conditions of the bile ducts and gallbladder. Ultrasound of the abdomen is a frequently used and is a relatively inexpensive and reliable test to evaluate for gallstones or blockage of the gallbladder. Magnetic resonance imaging (MRI) of the abdomen sometimes is done to look more closely at any obstructive disease of the biliary or pancreatic ducts.

What is the treatment for stool color changes?

The treatment for changes in stool color depends on the cause. As described previously, some changes in the color of stool can be due to the color of the ingested food. Other more significant medical causes may require simple or extensive medical evaluation and treatment.

Can stool color changes be treated at home?

As for self-care, it is important to recognize whether the change in stool color is persistent, recurrent, or transient (temporary). Generally, changes in stool color that are transient, for example, once or twice, and then return to healthy stool color are not as important as persistent or recurrent changes.

Some of the symptoms associated with changes of stool color also are important to recognize. For example, if the stool is red, maroon or black, it is suggestive of bleeding from the intestines, Symptoms of abdominal pain, lightheadedness, or dizziness (from losing too much blood) may require medical care more urgently.

What is the medical treatment for stool color changes?

Medical treatment for changes in stool color can vary widely depending on the cause. Examples may include:

  • Some common scenarios include gastrointestinal bleeding resulting in red, maroon, or black looking stool. In most cases, these are dealt with by gastroenterologists either in-office or in a hospital setting. Depending on the patient's description, physical examination, medical history, and results of diagnostic testing, the doctor may decide to treat with medications for stomach ulcers or inflammation in the stomach or the intestines.
  • In some situations, a specific treatment may not be available for bleeding, and the patient may only be asked to stop taking medications that can promote further bleeding (such as aspirin or nonsteroidal anti-inflammatory drugs [NSAIDs], including ibuprofen [Motrin, Advil], or naproxen [Aleve]).
  • Sometimes medications are injected into the sites of the bleeding during endoscopic evaluations to help stop the bleeding. In rare situations where bleeding continues despite aggressive medical care, radiologists may pass catheters through the arteries and inject the smaller arteries that are feeding the site of bleeding with chemicals or beads to reduce the bleeding. Surgery may be required to remove part of the intestine that is the site of bleeding if more conservative measures fail.
  • Clay-colored or gray stools also are evaluated by gastroenterologists as well as surgeons. If the change in color is caused by a stone obstructing the bile or pancreatic duct, the gastroenterologist sometimes can remove the stone by performing an ERCP. In other cases, surgery may be necessary to remove a stone or a tumor.

Can changes in Stool color be prevented?

Prevention of change in stool color depends on the cause. Since stool color can change for a variety of reasons, any preventive measure for a particular cause may play a role in preventing further changes in stool color. For example, if the stool is black and tarry because of a bleeding ulcer, then avoiding medications that can cause bleeding, such as aspirin, may be a reasonable preventive measure. Alcohol abstinence can be a preventive measure against yellow stools resulting from undigested fat in stool due to pancreatic disease. On the other hand, some causes of changes in the color of stool, for instance, cancer of the pancreas, may not be entirely preventable.

What is the prognosis for a person with stool color changes?

The outlook for a person with changes in stool color varies with the underlying cause. For example, many causes of bleeding from the stomach or the intestines are benign, such as ulcers, and generally carry good prognoses while bleeding due to a cancer carries a less favorable diagnosis.

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Colon Cancer Symptoms

Colon cancer can exhibit itself in several ways. If you have any of these symptoms, seek immediate medical help. Signs and symptoms of colon cancer include:

  • Rectal bleeding
  • Blood mixed with the stool
  • Black or tarry stools
  • Weight loss
  • Abdominal pain
  • Constopation
  • Bloating
Reviewed on 10/18/2022
Penner, R. M. MD. "Patient information: Blood in the stool (rectal bleeding) in adults (Beyond the Basics)." UpToDate. Sep 03, 2015.

Previous contributing author: Siamak N. Nabili, MD, MPH