Black Stool [Melena]: What Does Black Poop Mean?

Black stools are medically called melena.

You may have wondered: Doing a ‘number two’ should result in a brownish stool, so why is my poop black? Let’s start by explaining why poop is brown colored in the first place.

Normal stool appears brown because of the action of bacteria and digestive enzymes on a pigment called bile. Bile is produced in the liver and secreted on food to help in the digestion of fat.

In this article, we would try to help you understand what black poop means, teach you other related symptoms and explain how it is treated.

Melena itself is not a disease but is an indicator of an underlying issue. In other words, black stool is a symptom.

Bonus: You can download our free poop checklist for a healthy gut below

What Does Black Poop Mean?

Black poop means there is a significant amount of blood in the stool.

I know you are probably thinking: isn’t blood red?

Surely, blood is red, but blood turns black when hemoglobin is exposed to certain acids, enzymes, and digestive juices. So, this black color tells us that the blood originated from an area where those acids and juices are present.

Upper digestive tract bleeding is the main cause of Melena.

Bleeding from the Esophagus, Stomach or the Duodenum (first part of the small intestine) causes black stools, as this blood is digested first then moves to the large intestine where it mixes with poop, turning it dark.

On the contrary, bleeding from the lower part of the digestive tract usually presents as hematochezia– the presence of bright red blood in stool.

Melena and hematochezia have one common factor- bleeding.

While melena is bleeding that occurs in the upper digestive tract that is altered by enzymes, hence turning the blood color black, hematochezia is bleeding that occurs in the lower digestive tract that is relatively not altered, hence its bright red color.

What Causes Black Stools (Melena)?

Now that we have learned what melena is and that it is caused by bleeding from the upper digestive tract, it’s time to answer what conditions cause melena.

The most common cause of upper digestive tract bleeding is peptic ulcer.

Peptic ulcer is an erosion of the lining of the stomach or the duodenum. This exposes the stomach or duodenal walls to the effects of the acid secreted by the stomach. It is often painful and is described as a ‘burning sensation in the upper part of the abdomen’.

Your stomach secretes a powerful hydrochloric acid. This acid in your stomach is very corrosive, its pH ranges between 1.5-3.5.

In practical terms, according to a study, the hydrochloric acid in your stomach is strong enough to even dissolve a razor blade. Due to this level of corrosiveness, the walls of your stomach secrete a defensive mucous layer to protect itself from its own acid.

If there is an increased acid production or if the defensive mucus barrier is compromised, the acid can erode the lining of the stomach or duodenum, resulting in ulcers. When blood vessels are affected, these ulcers can sometimes bleed, leading to melena or black stools.

Here are some causes of peptic ulcers:

  • Helicobacter pylori infection
  • Use of painkillers known as Non-Steroidal Anti-Inflammatory Drugs (NSAIDS). Examples of NSAIDS are Ibuprofen, Diclofenac, Aspirin, and Naproxen.
  • Drinking alcohol
  • Tobacco use
  • Stress
  • Use of steroids
  • Use of anticoagulants (drugs that prevent the clotting of blood)
  • Eating spicy foods

Peptic ulcers are not the only cause of upper digestive tract bleeding. Some other conditions that can lead to bleeding in the upper digestive tract and hence, melena, are:

  • Malignant Tumors of the upper digestive tract
  • Bleeding Esophageal Varices: These are dilated veins in the esophagus that could burst and bleed).
  • Hemophilia: A disease where blood clotting mechanism is impaired causing a relatively high likelihood of bleeding.
  • Gastritis: An Inflammation of the stomach.

What Other Symptoms Are Related To Black Stool?

Depending on its cause, melena could be accompanied by other symptoms. Using peptic ulcer as an example, the effect of the corrosion caused by the stomach’s acid, dark stools can be accompanied by a burning abdominal pain, nausea or vomiting of blood (hematemesis).

In general here are some symptoms that are related to the passage of black stools:

  • Abdominal Pain.
  • Heartburn.
  • Nausea
  • Vomiting
  • Hematemesis (Vomiting blood)
  • Bloating.
  • Appetite Changes.
  • Dizziness
  • Weight loss

Are Black Stools Dangerous?

The simple answer is Yes!

Upper Gastrointestinal tract bleeding could be quite dangerous. Especially when the bleeding remains active.

A physician should be consulted straight away when you notice dark stools, as supposedly small bleeds could turn into an emergency.

A visit to a physician is very necessary to ascertain if the bleeding is active, how severe it is and the cause of the bleeding. The doctor would also treat it and try to prevent a recurrence.

How is Black Stool Treated?

The treatment for black stools is dependent on what exactly its cause is. We had established earlier that black poop is not a disease but is a symptom of a disease. So, it is treated by taking care of its underlying cause.

 Black stool is treated by taking care of its underlying cause. Black stool is treated by taking care of its underlying cause.

Generally, a doctor would assess melena by asking several questions to try to understand what its root cause is. Questions like when it started; if there are other accompanying symptoms and if there has been a diagnosis of peptic ulcer in the past.

The doctor will also carry out a physical examination to assess blood levels and will examine the abdomen. The doctor may perform a digital rectal exam (gently inserting a lubricated gloved finger into the anus) to look for signs of the black stool or to check if there is fresh blood.

To help in achieving a diagnosis, some tests can be ordered like:

  • Blood tests
  • Stool microscopy
  • Esophagogastroduodenoscopy (EGD): A test that uses a camera to examine the upper digestive tract.

 The stool may be examined if a person presents to the hospital with melena (black stools). The stool may be examined if a person presents to the hospital with melena (black stools).

The most common cause of melena is peptic ulcer. It is usually medically treated using antibiotics and drugs that decrease acid secretion.

Severe cases of peptic ulceration may require surgical intervention and if there is massive blood loss, blood transfusions may be requested for.

This article would not be complete if we don’t discuss false melena. I am sure you are wondering what false melena is.

What is False Melena?

False Melena is the passage of dark stools that are not related to bleeding. It is usually caused by medication, supplements, food or some minerals.

Here are some causes of false melena :

  • Black licorice
  • Iron supplements
  • Blueberries
  • Bismuth subsalicylate  (Pepto-Bismol)

False melena is not usually of a significance, and should always be differentiated from ‘True’ melena.


Melena or dark stools is a symptom that should not be missed nor taken lightly.

Proper investigation and treatment of melena are necessary to avoid life-threatening complications.

Also, remember that checking your poop from time to time is not always gross!

P.S: You can download your free poop checklist for a healthy gut below.

Dr. Omiete Charles-Davies

Dr. Omiete holds a bachelor's degree in medicine and surgery. He's a licensed medical practitioner who loves to share health information in a simple manner. For fun, he loves to travel and experience new cultures.

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