What Does Black Poop Say About Your Gut Health?

It may seem a little, er, TMI—but the truth is that the color of your poop offers quite a bit of insight into your overall gut health, so it’s worth taking a look. And while there can be a range of "normal" when it comes to stool color (shades of green and brown are pretty typical, experts say), there’s one color that usually requires a check-in with your doctor: black poop.

“Black poop can have several causes ranging from dietary factors to more serious medical conditions,” explains Samantha Nazareth, MD, a gastroenterologist based in New York City. Here’s what to do if you spot black-colored stool the next time you "go," plus some of the most common diet or health culprits and your treatment options.

What does it mean when you have black poop? 

First, rest assured that black poop isn’t always a medical emergency. There can be some pretty simple explanations for dark-colored stools, particularly if you’ve been taking any of the supplements or medications listed below. But because there is a chance that black poop could signal a more serious medical condition, it’s absolutely worth letting your healthcare provider know what you’re experiencing. Here's a breakdown of some of the most common reasons for black stools:

1. You've changed your diet 

Have you been loading up on some new foods? Certain darker-hued ingredients, like black licorice, blueberries, and blood sausages, can affect the color of your poop, Dr. Nazareth says. It’s also possible for red foods (think: beets or anything made with red food coloring) to turn your poop a darkish red that you might mistake for black.

2. You've been taking iron supplements

If your healthcare provider has prescribed you iron pills for anemia (a condition that causes low red blood cell count) or another health problem, black, tarry stools that look almost dark green can be a possible side effect. “The most common benign cause [for black poop] is consuming iron supplements,” Dr. Nazareth says. Along with dark poop, iron pills can make you feel nauseous, constipated, or cause a metallic taste in your mouth. If these side effects bother you, let your provider know—they might recommend taking a smaller dose or switching to a different formulation.

3. You’ve been taking Pepto-Bismol

This over-the-counter medication is helpful for relieving digestive symptoms like nausea, diarrhea, or an upset stomach. But bismuth, the active ingredient in Pepto-Bismol, can also interact with small amounts of sulfur in your digestive system to turn your poop black. When bismuth and sulfur mix, a substance called bismuth sulfide forms, which might make poop darker than usual as it exits your body. Luckily, this is a harmless side effect, and your stool color should go back to its usual color a few days after you’ve stopped taking the medication.

4. You have gastrointestinal bleeding

Sometimes, black poop is a signal that gastrointestinal (GI) bleeding is happening, often due to some kind of disorder or another health condition. Some of these include the following:

• Peptic ulcers: sores on the lining of the stomach
• Gastroesophageal reflux disease (GERD): a chronic form of acid reflux where stomach contents flow back up into your throat
• Gastritis: inflammation of the stomach lining
• Stomach, esophageal, or colon cancer

Because some causes for GI bleeding are very serious, your provider will take this symptom equally seriously: “Black stool can be a medical emergency if it is due to GI bleeding, particularly if it is accompanied by symptoms such as dizziness, weakness, paleness, shortness of breath, or low blood pressure, which may indicate significant blood loss,” says Dr. Nazareth. If you experience black, tarry stools along with these symptoms, you should seek immediate medical attention, she adds.

The difference between "melena" and GI bleeding

While you might hear the terms "melena" and GI bleeding used interchangeably, they're not quite the same thing. "Melena refers specifically to black, tarry stools that result from digested blood, typically from bleeding in the upper GI tract," Dr. Nazareth says, which includes the esophagus, stomach, small intestine, and sometimes the right side of the colon. As this blood moves through your GI tract, it can exit in the form of black poop with a very distinct foul odor, which develops as blood is broken down in digestion.

GI bleeding, on the other hand, is a broader term that can include both melena (from upper GI bleeding) and hematochezia—bright red blood that emerges from the lower GI tract, such as the colon or rectum. Hematochezia is often referred to as “rectal bleeding,” and looks more like distinct blood in your poop rather than dark-colored stools.

Other symptoms that may come with black poop

Like many digestive issues, black poop may come with some other unpleasant symptoms, too. These symptoms will often vary depending on the cause. While you should always talk to your provider rather than self-diagnosing, here are some other symptoms to watch for based on the most common black stool causes.

If it's from iron supplements:

• You may feel pain in your back, groin, muscles, chest, or sides
• You may feel dizzy or have chills
• You might notice a metallic taste in your mouth
• You might feel nauseous or vomit
• You might develop a fever, headache, or flushing

If it's from taking Pepto-Bismol:

• You may notice that your tongue is also black (this is also caused by the active ingredient coming into contact with sulfur in your saliva)

If it's a result of GI bleeding:

• Your poop may have a noticeably sticky consistency or odor, both of which can be typical of melena
• You may feel nauseous and possibly vomit
• You may have abdominal pain
• You may have shortness of breath, or feel very weak and fatigued

Keep in mind that symptoms of GI bleeding warrant a call to your healthcare provider right away.

There are a variety of treatment options

Your treatment options for black-colored stools vary greatly depending on what’s causing them. Sometimes, the best course is to wait and see: If you and your provider believe that diet or supplements are the culprits, “eliminating the offending substance can help you determine whether that was the cause,” Dr. Nazareth says.

But if your provider is concerned that your black poop may be a sign of GI bleeding, they’ll likely want to run a few tests to reach a diagnosis. That may include blood or imaging tests, as well as an endoscopy—a procedure that involves sending a thin tube with a camera down into your esophagus and stomach.

After that, subsequent treatments will depend on your diagnosis. Your medical team will work to come up with a plan to both address and stop the blood loss you’ve experienced, as well as the source of the bleeding itself. For example, your provider might opt to do a procedure to seal the wound in your GI tract, or if you've lost a lot of blood, you may need a blood transfusion (i.e., a procedure where you receive donated blood), too.

When to see a healthcare provider

If you notice your poop is black and think it's from recent diet and supplement changes—say, for example, because you took Pepto-Bismol or ate an unusual amount of black licorice (no judgment!)—you can probably wait to see if your bowel movements go back to normal in a few days, though it's still a good idea to let your healthcare provider know what's going on just in case.

But because black poop can also be a sign of a more serious health condition, it’s almost always best to err on the safe side and seek medical care right away. That’s especially true if you also have:

• Abdominal pain (this can be a sign of ulcers or certain cancers, Dr. Nazareth says)
• Nausea or vomiting, especially if you’re vomiting blood or contents that look like coffee grounds
• Unintentional weight loss 
• Fatigue, dizziness, or lightheadedness
• A strong pungent odor with your black poop (this is typical of melena, according to Dr. Nazareth) 
• Shortness of breath or palpitations (i.e., irregular heartbeat)
• Pale skin