EnglishEspañol

Why Is Your Poop Black and Tarry?

Written by Stephanie Watson
Medically Reviewed by Jabeen Begum, MD on February 16, 2025
7 min read

Sometimes, people have poop that's so dark it looks black. It might also have a sticky consistency, like that of tar. If your poop is black, it might be due to a change in your diet , a new medicine you're taking, or a medical problem that you don't want to ignore.

It's not unusual for poop to take on different colors, including all shades of brown, yellowish, and sometimes green. It's usually due to foods you've eaten, medications you've taken, and how much bile (a greenish digestive fluid) it contains. But poop that looks black or bright red can be a sign of bleeding. So, even if you think you know why it's happening, always call your doctor if you have black poop.

Often, black poop signals that there's bleeding in your digestive tract. Bleeding can result from:

  • An injury or tear in the lining of your digestive tract
  • A tear in your esophagus (the tube that connects your mouth and stomach) from intense vomiting
  • A bleeding ulcer (peptic ulcer disease)
  • Serious inflammation in your stomach lining (gastritis) or esophagus (esophagitis) 
  • Swollen, twisted veins (varices) in your stomach or esophagus
  • Erosion of the lining of your stomach (acute hemorrhagic erosive gastropathy), which can be caused by heavy drinking, high doses of nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen, or cancer treatments like chemotherapy
  • Cancer in your esophagus, pancreas, or stomach
  • A viral hemorrhagic fever like ebola

But other, less harmful things can cause it, too. They include:

  • Medicines that contain bismuth subsalicylate, an ingredient used to treat stomach problems like diarrhea
  • Activated charcoal, a black, powderlike substance that's used to treat some types of poisoning and is also sold as a supplement
  • Dark-colored foods, such as black licorice and blueberries
  • Iron supplements

Black or very dark green poop can be a side effect of iron pills you take for anemia , a condition that happens when you don't have enough red blood cells to carry oxygen around your body. This side effect isn't harmful, but call your doctor if:

  • Your poop also seems tarry.
  • You see red streaks in your poop.

Iron supplement side effects

Other possible side effects of iron supplements are:

To reduce the odds of side effects, always follow your doctor's instructions for taking your iron supplements. Tell your doctor if you have side effects that bother you. They may suggest another type of iron supplement that works better for you.

Some dark or deeply colored foods and drinks can temporarily turn your poop black. These include:

  • Black licorice
  • Chocolate sandwich cookies
  • Blood sausage
  • Blueberries
  • Grape juice
  • Beets
  • Foods or drinks that contain artificial coloring
  • Dark leafy vegetables
  • Dark beer

The dark color should go away once you stop consuming the food or beverage that caused it.

Bismuth subsalicylate is an ingredient in medicines you take for diarrhea, heartburn, and upset stomach. It works by easing inflammation in your intestines and reducing the flow of fluids into them.

One of the best-known medications containing bismuth subsalicylate is Pepto-Bismol. Others include:

  • Bismatrol
  • Diotame
  • Kaopectate
  • Kapectolin
  • Kola-Pectin

Why does it cause black poop? Bismuth subsalicylate combines with sulfur found in your saliva and digestive tract to form a black substance called bismuth sulfide. It leaves your body as black poop.

Your poop should return to normal after you stop taking medicines that contain this ingredient, but it might take a few days.

Black, tarry poop with an unusually bad smell is often a sign that you have bleeding in your esophagus, stomach, or the top part of your small intestine. The blood turns black and tarry when it's digested in your gastrointestinal tract. If you have bleeding lower in your digestive tract, your poop may look red.

Several different medical conditions can cause the type of bleeding that leads to black poop, ranging from a tear in your esophagus to stomach cancer. Internal bleeding is a serious condition that requires medical treatment.

What Is melena?

Melena is the term doctors use to describe black poop that you get due to bleeding in your digestive system. Your doctor can test your poop to see if it contains blood. If they find it, they'll need to do further tests, such as blood tests and imaging tests, to see what's causing the bleeding.

Melena treatment

Melena is not a condition itself, but a symptom of bleeding in your digestive tract. What treatment you'll need depends on what's causing it and how serious it is.

Your doctor may take these steps:

  • Stop the bleeding. They may use stitches, medication, a band or clip, or electrocautery (heat from an electric current) to do this.
  • Treat your blood loss, if needed, with IV fluids or a blood transfusion.
  • Treat the condition that led to bleeding. For inflammation, erosion, or an ulcer, they might use acid-blocking drugs. Other causes may require more intensive treatment.

A peptic ulcer is one of the most common causes of melena. An ulcer is an open sore on the inside of your stomach or small intestine. Sometimes these sores bleed, which can make your poop dark.

You get peptic ulcers when digestive acids damage the lining of your stomach or intestine. Some things that can cause this are:

  • Inflammation that results from a bacteria called H. pylori
  • Overuse or misuse of NSAIDs such as aspirin, ibuprofen, and naproxen

Ulcer symptoms

Other signs that you have an ulcer include:

Some medicines for ulcers lower the amount of acid in your stomach. Others coat your stomach and protect it from the damage acids can cause. Your doctor might also prescribe antibiotics to kill H. pylori. 

Call your doctor if you have black poop or:

  • See blood in your poop or vomit
  • Have trouble breathing
  • Feel like you're about to pass out
  • Have lost weight without trying
  • Lose your appetite

Black, tarry poop is sometimes a sign of esophageal or gastric cancers.

Why does cancer cause black poop?

Tumors often bleed, and internal bleeding leads to black poop. Tumors in the upper portion of your digestive tract are more likely to cause black poop than those lower down, as the blood gets exposed to digestive juices before it leaves your body.

Esophageal cancer symptoms

Some other symptoms of esophageal cancer are:

Gastric cancer symptoms

If you have gastric (stomach) cancer, you could also have symptoms such as:

  • Feeling tired
  • Being bloated after you eat
  • Serious heartburn or indigestion
  • Nausea or vomiting
  • Pain in your stomach
  • Losing weight without trying

Treatment for these cancers depends on the stage of the disease and how far it's spread. Options include surgery, chemotherapy, and radiation.

Intense coughing or vomiting can tear your esophagus and make it bleed. This condition is called a Mallory-Weiss tear.

Mallory-Weiss tear symptoms

Besides black, poop you might have these symptoms:

Most tears heal on their own. If yours doesn't, your doctor can use a heat treatment or give you medicine to stop the bleeding.

Call your doctor if you:

  • See a dark color in either your vomit or poop
  • Feel weak or dizzy
  • Are short of breath
  • Have pain in your chest or belly

Varices are swollen veins in your esophagus. They're more common in people with liver disease. These abnormal veins can sometimes leak blood or break open, leading to bleeding that turns your poop black. 

If varices are causing your black poop, you might also have symptoms such as:

  • Vomiting blood
  • Dizziness
  • Fainting

Bleeding in your esophagus is an emergency that requires treatment in a hospital. The treatment usually involves getting medicine through an IV to lower vein pressure or a procedure called an endoscopy , which involves tying off the veins to stop the bleeding.

Call your doctor if you:

  • Have blood in your vomit or have black, tarry poop
  • Get very dizzy or pass out

Sometimes, your poop isn't a solid dark color but has black flecks or spots. These black spots in your poop might be undigested bits of food, such as blueberry or black bean skins.

But these dark blotches can also be caused by the same things that cause overall black poop, such as eating dark foods, taking certain medications, and internal bleeding. Poop that looks dark brown and has a texture like coffee grounds can be a sign of older blood in your digestive tract.

You might have black poop because of something as simple as a change in your diet or a medicine you're taking. Sometimes, though, it's a sign of a medical problem that you don't want to ignore, such as bleeding in your digestive tract. You should always see a doctor if you have black poop, especially if it's also sticky or tarry.

Can dehydration cause black stool? 

Mild dehydration can lead to constipation and stool that's darker brown and harder than normal. But black, tarry stool is often a sign of bleeding in your digestive tract. 

What does unhealthy stool look like? 

Everyone's digestion is different, so what's normal and healthy can vary widely. What's most important is consistency. If you notice changes in the color, texture, or shape of your poop, or in how often you go, talk to your doctor. Also, contact your doctor anytime you have black poop or see red blood in your poop.

What does blood in the stool indicate? 

Blood in your stool indicates that there's bleeding in your digestive system. Your poop might look black and tarry, or you might see red blood in it. Call your doctor if this happens.

What causes bloating and black stool?

Black poop with bloating can be caused by several serious conditions, ranging from a bleeding ulcer to cancer. See your doctor if you notice either black poor or any new bloating or belly pain.