Melena: What Black, Tarry-Stool Means & When It's An Emergency

Dr. Debora Poli
Clinical review: Dr. Debora Poli Gastroenterology CRM-SP 114099
Created by: Daisy Oliveira Registered Nurse
Key points
  • Black, tar-like stool with a strong odor can be a sign of digested blood from internal bleeding and should be assessed urgently.
  • Vomiting blood, coffee-ground vomit, fainting, severe weakness, or paleness with melena can indicate significant blood loss.
  • Bright red or maroon blood in stool can also be serious, especially when it occurs with dizziness, fast heartbeat, or low blood pressure.

Melena is the passage of black, tar-like, foul-smelling stool caused by digested blood in the digestive tract. It is usually a sign of bleeding in the upper gastrointestinal tract, such as the esophagus, stomach, or duodenum.

This can happen due to conditions such as stomach ulcers, erosive esophagitis, gastritis, esophageal varices, or Mallory-Weiss syndrome. It can also occur after swallowing blood, such as from a nosebleed or after coughing up blood.

Because melena can indicate internal bleeding, medical evaluation by a gastroenterologist or general practitioner is important. Tests can help identify the cause and guide treatment to stop the bleeding and prevent complications.

Patient holding abdomen

Symptoms of melena

The main symptoms of melena are:

  • Dark, tar-like stools

  • Black, foul-smelling stools

  • Abdominal pain

  • Indigestion

In some cases, other symptoms may include fatigue, weakness, fainting, difficulty swallowing, or vomiting blood. If left untreated, melena can lead to complications such as anemia, loss of consciousness, and even multi-organ failure.

For this reason, it is essential to consult a gastroenterologist or general practitioner whenever symptoms of melena occur, so treatment can be started promptly.

Also recommended: Poop Color Meaning: Green, Black, Yellow, Red & White tuasaude.com/en/what-your-poop-means

Main causes of melena

The main causes of melena are:

1. Stomach ulcer

A stomach ulcer is a sore that forms on the stomach lining and can cause bleeding. Depending on the amount of blood released, stools may become very dark and foul-smelling. Ulcers are more common in people with chronic gastritis and are usually accompanied by other symptoms, such as severe stomach pain after eating, persistent nausea, and vomiting.

What to do: Treatment is prescribed by a gastroenterologist and typically involves medications that reduce stomach acid, such as omeprazole, esomeprazole, or antacids, to help ulcers heal. Dietary changes are also an important part of treatment.

2. Esophageal varices

Esophageal varices are enlarged veins in the esophagus that can rupture and bleed into the digestive tract, leading to very dark, foul-smelling stools. Other symptoms include vomiting bright red blood, paleness, and severe fatigue.

This condition is most common in people with liver disease, which increases pressure in the veins of the digestive system and causes them to dilate.

What to do: Immediate medical care is required, as ruptured esophageal varices are a life-threatening emergency that usually requires surgery to stop the bleeding. Ongoing treatment as directed by a doctor is also necessary to prevent recurrence.

3. Gastritis

Gastritis is inflammation of the stomach lining. While it often does not cause bleeding, untreated gastritis can irritate the lining enough to cause small bleeds, leading to melena. Other symptoms may include stomach pain, heartburn, general discomfort, and vomiting, especially after eating.

What to do: Gastritis treatment is managed by a gastroenterologist with medications such as omeprazole or esomeprazole. If melena is suspected, a medical evaluation is important, since bleeding may also indicate a developing ulcer.

Check-out some home remedies for gastritis that can be prepared to complement your treatment.

4. Erosive esophagitis

Erosive esophagitis is inflammation, irritation, or swelling of the esophagus lining, which can cause sores that bleed and result in melena. Other symptoms may include vomiting blood, chest pain, heartburn, or throat pain when swallowing.

This condition is usually caused by frequent acid reflux or untreated esophagitis, as stomach acid rising into the esophagus can damage the lining.

What to do: Treatment should be guided by a gastroenterologist to prevent lesions and bleeding. In cases of bleeding, treatment in the hospital may include intravenous proton pump inhibitors and surgery to stop the hemorrhage.

5. Mallory-Weiss syndrome

Mallory-Weiss syndrome occurs when small tears develop in the esophagus due to excess pressure, often after repeated or forceful vomiting. These tears can rupture blood vessels, leading to bleeding and melena. Common symptoms include vomiting blood, pain in the upper stomach, extreme fatigue, dizziness, or fainting.

What to do: Hospital evaluation is recommended to stop the bleeding and begin treatment. In more severe cases, surgery may be needed to repair the tears.

6. Stomach cancer

Although less common, stomach cancer can cause melena due to bleeding in the stomach lining. Other signs and symptoms may include unexplained weight loss, persistent heartburn, loss of appetite, feeling full after eating small amounts, and severe weakness.

What to do: Any suspicion of stomach cancer should be evaluated by a gastroenterologist as soon as possible. Early detection improves treatment success. Most cases are treated by an oncologist with chemotherapy and radiation therapy, and surgery may be necessary to remove the affected part of the stomach.

7. Medication use

Certain medications can irritate or damage the digestive tract and cause melena, including:

What to do: Go to the hospital for evaluation and treatment, which may involve medications or surgery to stop the bleeding. The doctor may also adjust or replace the medication responsible and prescribe stomach protectors if necessary.

Difference between melena and hematochezia

Difference between melena and hematochezia

Melena and hematochezia are both signs of gastrointestinal bleeding, but they differ in stool color, bleeding source, and how long blood remains in the digestive tract.

Feature Melena Hematochezia
Basic definition Passage of black, tar-like stools containing digested blood. Passage of bright red or maroon blood from the rectum, often mixed with or coating stool.
Typical color Black or very dark, often tar-like and shiny. Bright red or dark red/maroon blood.
Consistency and odor Sticky or tar-like stool, usually with a strong, characteristic foul smell. Blood may appear on toilet paper, in the toilet bowl, or mixed with stool. Odor is less specific.
Main bleeding source Usually the upper gastrointestinal tract, such as the esophagus, stomach, or duodenum. Usually the lower gastrointestinal tract, such as the colon, rectum, or anus.
Important exceptions It can rarely come from bleeding in the right side of the colon if stool moves slowly enough for blood to be digested. Massive, rapid upper gastrointestinal bleeding can sometimes cause bright red blood from the rectum.
How it happens Blood stays in the intestine long enough to be digested and oxidized, giving stool its black color. Blood moves quickly through the bowel, so it remains fresh and red.
Common causes Peptic ulcer disease, erosive gastritis or duodenitis, esophageal or gastric varices, Mallory-Weiss tear, and upper gastrointestinal cancer. Hemorrhoids, anal fissures, diverticular disease, colonic polyps or cancer, colitis, and angiodysplasia.
Associated symptoms May occur with vomiting blood, coffee-ground vomit, upper abdominal pain, fatigue, paleness, low blood pressure, or fast heart rate if bleeding is significant. May occur with abdominal cramps, diarrhea, changes in bowel habits, anal pain or discomfort, and signs of blood loss if bleeding is heavy.
Initial diagnostic test Upper endoscopy is usually the first test used to locate and treat the bleeding source in stable patients. Colonoscopy is usually the first test used to evaluate the colon and rectum. Anoscopy or sigmoidoscopy may be used for bleeding near the anus or rectum.
Clinical urgency Melena is always considered a potentially serious sign of internal bleeding that needs urgent assessment.

Hematochezia can also be serious, especially when bleeding is heavy or occurs with weakness, fainting, or low blood pressure.

In melena, bleeding occurs in the upper digestive tract, such as the stomach, mouth, esophagus, or duodenum. Because the blood is digested as it passes through the intestines, stools appear dark and tar-like.

In hematochezia, bleeding occurs in the lower digestive tract, such as the small intestine, colon, rectum, or anus, resulting in bright red blood in stool.

Update History
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