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Black or Tarry Stools - Causes, Diagnosis, Prevention and Treatment

Published on Sep 21, 2019 and last reviewed on Feb 06, 2021   -  4 min read


Black or tarry stools can be due to change in diet, or it can be a sign of some underlying medical condition. Read about all the possible causes and treatment options.

Black or Tarry Stools - Causes, Diagnosis, Prevention and Treatment

Black or tarry stool is not always something to panic about. Many common causes like food, iron supplements, and other medicines can make your stool appear black. When food is not digested properly in the stomach because of some surgery or you eat licorice and beet, your stool will appear black or red. Black stool does not always mean you are bleeding internally. But, if you notice that your stool is black and has a foul smell often, then it is best to consult a doctor, as it can also be caused due to bleeding or injury in your gastrointestinal tract. So if you notice a change in color, always consult your doctor so he or she can rule out if blood is present in the stool with a simple test. Black stool that results from bleeding is called melena.

Points to Remember:

  1. The most common cause is eating dark foods or iron supplements.

  2. Bleeding ulcer also commonly causes melena.

  3. Blood in stools indicates an upper gastrointestinal problem.

  4. A stool test can detect blood in stools.

  5. Always consult your doctor if your poop is black and you have vomiting or diarrhea.

What Are the Causes of Black or Tarry Stools?

Some of the common causes are:

How Can the Cause of Black or Tarry Stools Be Diagnosed?

After taking a complete medical and family history, your doctor will perform a physical examination to determine the cause. The doctor might tell you to perform the following tests:

What Are the Treatment Options Available for Black Stools?

Treatment for black stools depends on the cause. Treating the underlying condition will treat this problem. The treatment options include:

Too much bleeding can result in severe anemia, which can also be fatal. If you have developed severe anemia, a blood transfusion might be necessary.

How Can Black Stools Be Prevented?

Some of the causes of black stools can be prevented by:

If the cause is food, then black stool is not a problem. If it is accompanied by other symptoms, then consult a doctor online.

Frequently Asked Questions


What Does a Black Stool Indicate?

Black stools are termed as “melena.” Black stools most often indicate the presence of upper gastrointestinal tract bleeding. There can be many causes for upper digestive tract bleeding like peptic ulcer disease, a tumor, or liver disease, etc. Black stools can also be caused by the intake of certain medicines like iron supplements.


What Does Tarry Stool Look Like?

The appearance of black tarry stools is because the red blood cells that are released from the bleeding site are broken down by the digestive enzymes. This process turns the stool black. A dark tarry stool looks very sticky, and it is very foul-smelling. Thus, gastrointestinal bleeding is a medical emergency, and if a person notices his or her stools with these features, immediate medical treatment is necessary.


Should I Worry If My Stool Is Black?

Black stools can be caused by varied reasons, the simplest reason would be the intake of dark-colored foods, and the most severe cause could be ongoing gastrointestinal bleeding. It is mandatory for the doctor to rule out internal bleeding when you have a black stool. When you have other symptoms like vomiting, pain, and diarrhea, immediate medical care is needed. Therefore, the black stool is something you have to worry about.


What Medications Cause Black Stool?

Medications that cause a patient to present with black stool are iron supplements, activated charcoal, and medicines that contain bismuth in them. Therefore, when a doctor prescribes these kinds of medications to patients, it is necessary to educate the patients about black stools. This will avoid unnecessary fear in patients.


How Long Does Black Stool Last?

When the black stools are induced due to the intake of medicines, it might last during the complete period of medications. Also, it will last up to several days, even after the patient has stopped taking the medicines. But, when the cause is upper gastrointestinal bleeding, the black stools might only cease when the bleeding is treated and stopped. The condition of the patient might progressively deteriorate if the cause is not treated.


What Foods Cause Black Stools?

Intake of certain foods leads to the formation of black stools. Those foods are blackberries, blood sausages, dark chocolates, and black licorice. Thus, when patients come to the clinic with a history of intake of these foods, it is important for the doctor to ensure that it is normal. If not, then the patient should be checked for any other medical conditions.


What Does Black Tarry Stools Mean?

The black tarry stool is a common term that is used to explain when a person states where the stools look dark black in color. It is usually foul-smelling and very sticky in nature. This makes it appear like black tar. Thus, these stools are called as black tarry stools.


What Are Tarry Dark Stools?

Tarry dark stools are the presentation of stools when the person is affected with upper gastrointestinal bleeding. The digested RBC’s are turned to black color in the process. Thus, when dark tarry stools appear, and it is a medical emergency. Prolonged bleeding can even lead to the death of the person. You should consult your doctor immediately if you are suffering from such a health problem.


Why Is My Poop Thick and Sticky?

Sticky stools are either pale and greasy or dark and tarry. The common cause for this texture is increased fat intake in the diet or the presence of gastrointestinal bleeding. It can also be a result of a chronic digestive disorder. It can be accompanied by symptoms like bloating and abdominal cramps. It is always necessary that you consult with your doctor and rule out the presence of any life-threatening disease conditions.


What Is Black Tarry Stool a Sign Of?

The black tarry stool is a sign of upper gastrointestinal bleeding predominantly. It is rarely an indication of lower gastrointestinal bleeding. It occurs when the bleeding of the gastrointestinal tract releases red blood cells. Those red blood cells get digested by the digestive enzymes, resulting in the formation of black tarry stools.


Is Black Tarry Stool an Emergency?

Yes, Black Tarry stool is an emergency because it indicates the presence of upper gastrointestinal bleeding. Negligence of this condition might be harmful. You should rush to the doctor and seek medical help as soon as possible.


When Should I Be Concerned About Black Stool?

Since black stools are an indication of upper gastrointestinal bleeding, this can be due to ongoing bleeding. Ongoing bleeding can lead to the condition of the patient to progress to anemia. This is a fatal condition. Thus, immediate care and proper attention should be given when you have a black stool. Hospitalization might be needed if the cause is confirmed by the doctor to be gastrointestinal bleeding.


Can Dehydration Cause Dark Stools?

Yes, dehydration can cause dark stools. Especially in conditions where the patient experiences vomiting and fever, the person might become progressively dehydrated. Thus, adequate fluid intake is essential to prevent dehydration. Rehydration can prevent dark stools. But preventing dehydration alone is not a solution when the primary cause is gastrointestinal bleeding.


What Foods Cause Dark Stools?

Foods that cause dark stools are beetroots, dark chocolates, blueberries, blackberries, etc., It is normal if you get black stools after eating these foods. It does not need medical treatment as it will resolve on its own. However, if the cause does not seem to be food, it is a medical emergency.


Is Black Stool Life Threatening?

Yes, having black stools is a life-threatening condition, because it is caused due to gastrointestinal bleeding. Prolonged gastrointestinal bleeding might lead to hemorrhagic shock in the patient. It might be fatal. Thus, immediate medical treatment is mandatory.


Can Stress Cause Black Stool?

Stress cannot cause black stools directly. Excessive levels of stress can result in gastrointestinal problems such as gastritis. When a person is suffering from gastritis, he will experience symptoms such as abdominal pain, nausea, vomiting, bloating, and black colored stools. These symptoms might result in other symptoms, such as black stools. This could be dangerous, and you need to report to the doctor immediately.


What Causes Black Stool During Pregnancy?

Pregnant patients might be taking Iron tablets. This might cause black stools. Some medications might contain bismuth subsalicylate. These medications might make the stools appear black. It is proved that some foods with black food colors can result in tarry and black colored stools.


Does Your Period Affect Your Poop?

Periods have a strong influence on the changes of the stools. There will be an increase in the levels of progesterone during the menstrual cycle. Also, the prostaglandin levels would have reduced, resulting in periods of constipation. Some women experience dysentery during their periods. It is because the menstruation hormones lead to the contraction of nearby muscles and intestines. This will lead to constant defecation in women.

Last reviewed at:
06 Feb 2021  -  4 min read




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