Black bowel movements


Black stool usually indicates a particularly dark color of the stool.

Often the causes can be found in the diet or medication. If this is not the case, bleeding in the gastrointestinal tract must first be considered. Black stool, depending on the cause of the change in stool, can be accompanied by both diarrhea and particularly hard stool.

Physiologically, newborns usually have black stools. With them, the first bowel movement, which is also known as child spank because of its color, is colored black due to the amniotic fluid it contains.

Read more in our main article: Colors of bowel movements

Causes of Black Stool

Below is an overview of the most important causes of black stools. These are explained individually below.

  • Food

    • Food coloring

    • red wine

    • Dark berries

  • Medication

    • Iron tablets

    • Painkiller

    • Antibiotics

  • Bleeding

    • Bleeding from the esophagus such as variceal bleeding

    • Bleeding in the stomach, including from ulcers

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Taking iron tablets

Iron tablets have a particularly large number of side effects in the gastrointestinal tract due to the difficult digestibility of iron.

Taking iron tablets, for example, often leads to diarrhea or constipation as well as abdominal pain. In addition, the stool is often colored black due to the iron tablets. Since iron tablets usually have to be taken over a long period (three to six months), the symptoms can last for a long time.

After stopping the iron tablets, the black stool may persist for a few weeks, after which the color of the stool should return to normal.

Food coloring

Food coloring is a chemically produced substance that tends to be difficult to digest and can therefore stain stool in a wide variety of colors.

In particular, dark colors such as black, purple, blue, and green can make the bowel movements dark and lead to black bowel movements. Most of the time, stools are black one to two days after ingesting the food coloring. The symptoms can last for a few days and should then go away completely.

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red wine

Red wine contains a particularly large number of dark coloring substances that are not absorbed into the body during digestion.

Especially with regular red wine consumption or large quantities of red wine, these dyes can accumulate and discolor the stool. Usually, a glass or two of red wine should not turn stools black. With a larger amount of red wine and thus a corresponding amount of the dark dye, the stool may temporarily be dark to black in color. After a few days, the color of the stool should return to normal.

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Gastrointestinal bleeding

Bleeding in the gastrointestinal tract can present itself as red, dark or black deposits on the stool or even completely colored.

A distinction is made between fresh bleeding that occurs in the last sections of the intestine and that are manifested by bright red blood deposits. In contrast, blood becomes dark especially when it has already clotted. If the blood is digested by the stomach acid, it can turn black. Therefore, black stools and deposits on the stool are suspicious of bleeding in the stomach or esophagus.

More information on this topic:

  • Esophageal variceal bleeding

Taking painkillers

Painkillers, especially the non-steroidal anti-inflammatory drugs such as ibuprofen, diclofenac and ASA (Aspirin®) have other effects in the body in addition to their analgesic function. They lower fever and thin the blood slightly (especially aspirin) but also inhibit the formation of the protective gastric mucus. This can cause the acid to damage the lining of the stomach.

The combination of damage to the gastric mucosa and the slight thinning of the blood occasionally lead to gastric ulcers and gastric bleeding. This can lead to black stool. To prevent bleeding, painkillers are combined with stomach-friendly tablets if they have to be taken over a longer period of time. These ensure a reduced acid production and thus protect the stomach.

More on this:

  • Symptoms of a stomach ulcer

Black stool from antibiotics

Antibiotics have a particular impact on the digestive tract. The active ingredients are specifically directed against bacteria. In doing so, they not only attack the pathogens against which they are ingested. Instead, the intestinal bacteria, which play a key role in digestion, are attacked by the antibiotics, which changes the composition of the so-called microbiome (total amount of bacteria in the digestive tract).

This invasion of the bacteria in the intestines can cause major changes in bowel movements. Often there is diarrhea or constipation. Taking antibiotics is also often associated with abdominal pain, sometimes with nausea, vomiting and flatulence. It is not uncommon for the color of the bowel movements to change, often the bowel movements become yellowish or green, but the green color can also turn into a very dark hue or even black.

It is important to differentiate the cause of black stool between intestinal bleeding and the side effects of antibiotic therapy. The black color of stool usually disappears a few days after stopping antibiotic therapy. However, the antibiotic can also cause inflammation of the bowel, which also causes bleeding. In the event of pain and suspicion of this, a doctor should be examined.

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  • Pseudomembranous colitis as a side effect of antibiotics

Can the pill cause black stools?

Black stools are not considered a side effect of the pill, so the discoloration of the stool should not usually be linked to the drug.

If the bowel movement occurs frequently immediately after taking the pill, an intolerance to substances in the pill should be considered. Under certain circumstances, this can prevent the pill from working properly. Even if diarrhea immediately follows the pill, one must reckon with the fact that the active substance cannot be completely absorbed into the body, so that there is no adequate contraceptive protection.

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Can that be an indication of cancer?

Black stool can generally be an indication of cancer and tumors (benign as well as malignant).

The black stool is also caused by tumor diseases, mainly due to clotted and digested blood. Usually the source of the bleeding is in the esophagus or stomach. Therefore, black stools can also indicate esophageal cancer or stomach cancer. Basically, the esophagus and stomach should be examined for sources of bleeding if the stool is black. A biopsy (tissue sample) can also be taken, which can be used to identify cancer cells.

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This is how black stool is diagnosed

If the stool is black, the anamnesis (doctor-patient conversation) is indicative. The doctor should ask whether the black stool could have been caused by food, for example.

Otherwise, a physical exam of the abdomen should be done. An ultrasound should also be performed. Blood tests in the laboratory can also provide clues as to the cause of the disease.

A gastroscopy can also be performed, which involves inserting a camera through the esophagus into the stomach. In this way, a source of bleeding can be identified and possibly treated directly.

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  • A gastroscopy procedure

What symptoms can you tell that the black stool is pathological?

In most cases, black stools are suspect.

Especially when it comes to the typical tarry stool caused by clotted and oxidized blood in the stool. This is usually not only noticeable through the conspicuous coloring. In addition, there is usually a clearly strong odor in the stool. Even if the stool itself is not completely black, but only black deposits on the stool, this is already suspect.

Black stool that is not due to changed eating habits or the ingestion of dark foods can always tend to be pathological. Occasionally, the black stool is caused by medication that is particularly rich in iron or carbon. However, if such drugs are not taken, one should assume a pathological cause in the case of black stools. Especially if there are factors that can promote bleeding in the stomach and esophagus. This includes taking painkillers as well as therapy with blood thinners. If, in addition to black stool, other symptoms such as nausea, vomiting, diarrhea, constipation or general symptoms such as weight loss, poor performance, fatigue etc. occur, the black stool is also suspect.


Diarrhea is a very common symptom of the gastrointestinal tract.

Typically, there is increased bowel movements (at least three times a day) and a soft to liquid consistency. The stool may also be discolored. Diarrhea can be caused by certain foods as well as medication. Infections of the digestive tract can also cause diarrhea. If you have black stools in connection with diarrhea, you should think of chronic inflammatory diseases; these often cause liquid stools and can also lead to bleeding, which turns the stool black.

Also read:

  • Causes of diarrhea


Flatulence is mostly based on an imbalance in the digestive bacteria in the intestine.

If this so-called microbiome is changed in its composition through external influences, this can affect the function of the bacteria. As a result, the intestinal bacteria produce more gases, which become noticeable in the form of a distended intestine. The flatulence allows the increased air to escape from the intestine. Often gas and black stools occur with antibiotic therapy or the intake of iron tablets.

Also read:

  • Causes of Flatulence
  • Home remedies for flatulence

stomach pain

Abdominal pain is a very unspecific symptom that is not necessarily caused by the digestive tract. However, black bowel movements must be thought of as having a cause in the gastrointestinal tract.

Abdominal pain can mainly be triggered by medication such as iron tablets, which also turn the stool black. However, sources of bleeding such as a stomach ulcer can also lead to black stools and abdominal pain. In this case, the abdominal pain is often dependent on food intake.


Constipation occurs when there is not enough fluid in the bowel movement. This solidifies the bowel movements and makes emptying the bowel particularly difficult.

However, constipation can also be caused by obstructions in the bowel. For example, if there is a tumor in the bowel area, the stool can no longer be transported to the end of the bowel and constipation occurs. When constipated, the intestine becomes very irritated, which can cause the dark or black color of the stool.

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When does black stool require treatment?

If the black stool is due to bleeding, it will in most cases require treatment. On the one hand, the source of bleeding should be stopped. This can be done both medically and interventionally. The bleeding can often be treated during the diagnosis and thus the discovery of the bleeding source during endoscopy. Concomitant symptoms such as anemia and iron deficiency due to the bleeding must also be treated. Iron tablets are usually sufficient for this, but a blood transfusion may be necessary if there is severe blood loss.

If the bowel movement is caused by chronic diseases such as inflammatory bowel disease or a tumor, therapy must also be given. The treatment of a chronic inflammatory bowel disease such as Crohn's disease or ulcerative colitis is usually a long-term therapy. Tumors (both benign and malignant) can be treated surgically; if necessary, further oncological therapy with the administration of chemotherapeutic agents must be carried out.

If the black stool is caused by infectious diseases, the decision on therapy is made based on the severity of the symptoms. If the symptoms are mild, no therapy is necessary; if the symptoms are severe, such as significant dehydration, adequate fluids should be given. Antibiotics against the bacteria that caused the infection may be necessary. This in turn can cause further complaints.

More information on this topic:

  • Therapy of a gastric ulcer
  • Therapy of Crohn's disease
  • Home remedies for a gastrointestinal infection

Duration and prognosis of black stool

The duration and prognosis of black stools vary greatly depending on the cause of the symptoms.

Harmless causes such as the absorption of the dye through food or the coloring from medication have a very good prognosis, and the symptoms disappear after a few days (with medication, a few days after discontinuation). Infectious diseases usually only change bowel movements for a few days.

Chronic illnesses, on the other hand, result in long-lasting black bowel movements, which often do not go away without treatment or often return. Serious illnesses such as tumor diseases or serious organ malfunctions can have a negative impact on quality of life and possibly also lifespan.

Black chair at the baby

Black stools in babies can be both normal and very worrying.

Basically, the newborn's first bowel movement is black. The color is caused by the high proportion of amniotic fluid that is contained in this stool. Because of its color, the baby's first bowel movement is also known as child pecking. If, on the other hand, this bowel movement does not occur, the child should be examined for malformations or other diseases in the gastrointestinal tract.

After the first few days of the newborn period, black stools should no longer occur in the baby. In general, baby's bowel movements can take on many colors, so a very dark stool is not uncommon. A deep black coloration with a noticeable odor, on the other hand, is not normal in babies either and should therefore be examined.

Read more on this topic:

  • Kindspech- The child's first chair
  • Defecation in the baby

Black chair in the child

Black stool usually does not occur in children. However, it can be caused by changes in eating habits or very dark-colored foods, for example. If the black stool no longer persists after a day or two, there is usually nothing to worry about.

The most common cause of dark to black stools in children is gastrointestinal infections. In addition to diarrhea, abdominal pain, nausea and vomiting, these can also cause black stools.