What Black Poop Could Mean for Your Gut Health

It’s not exactly dinner-table conversation, but what ends up in the toilet bowl can tell you a lot about your gut health. While stool can vary in color and texture from day to day, black poop is one shade that tends to raise eyebrows and for good reason.

Although it doesn’t always signal something serious, black-colored stool is one of those symptoms your healthcare provider wants to know about. Here’s what black poop might mean, and how to know whether it’s time to get it checked out.

What Black Poop Might Be Telling You

Stool usually falls within a spectrum of browns and greens, thanks to bile and how food is digested. When things turn black, though, it can be the result of a few different causes some harmless, and others more serious.

1. It Could Be Your Diet

Foods like black licorice, blueberries, or even meals made with a lot of red food dye can darken your stool. Blood sausages or dark leafy greens may also play a role. Red-colored foods may appear darker after digestion, sometimes giving the illusion of black poop.

2. Iron Supplements Are a Common Culprit

Iron pills, often prescribed for anemia, are known to cause stool to darken sometimes to a tarry, almost black-green hue. It’s a harmless side effect, but it may also come with nausea, constipation, or a metallic taste. If the side effects bother you, talk to your provider about adjusting your dose or switching brands.

3. You’ve Taken Pepto-Bismol

Bismuth subsalicylate, the active ingredient in this popular pink remedy, can combine with sulfur in your digestive tract and turn your stool (and sometimes your tongue!) black. This effect is temporary and nothing to worry about but your poop should return to normal within a few days of stopping the medication.

4. It May Be a Sign of Gastrointestinal Bleeding

Here’s where black poop can indicate a more urgent issue. If you notice black, tarry, or sticky stools with a strong, foul odor, it could be melena a sign of upper gastrointestinal bleeding, which can result from:

• Peptic ulcers

• Gastritis (inflammation of the stomach lining)

• Gastroesophageal reflux disease (GERD)

• Esophageal or stomach cancer

“Black stool can be a medical emergency if it’s due to GI bleeding,” says Samantha Nazareth, MD, a New York-based gastroenterologist. If it’s accompanied by dizziness, paleness, fatigue, shortness of breath, or fainting, seek care immediately.

Melena vs. GI Bleeding: What’s the Difference?

• Melena: Specifically refers to black, tarry stool caused by digested blood, typically from the upper GI tract.

• GI Bleeding: A broader term that includes both melena and hematochezia bright red blood in stool from the lower GI tract, such as the colon or rectum.

Both deserve medical attention, but melena can indicate slow, chronic bleeding that might not be noticed right away.

Other Symptoms to Watch For

Depending on the cause, black poop may be accompanied by:

• From Iron Supplements: Back or muscle pain, dizziness, chills, nausea, vomiting, or a metallic taste.

• From Pepto-Bismol: A black tongue (harmless and temporary).

• From GI Bleeding: Sticky stool with a strong odor, nausea, vomiting (possibly with blood or coffee ground-like material), abdominal pain, weakness, fatigue, and pale skin.

When to See a Doctor

If you can link your dark stool to diet or a new medication (like iron or Pepto-Bismol), monitor it for a few days. If the color fades once you stop the suspected cause, you’re likely in the clear.

But reach out to your provider immediately if you experience:

• Persistent black or tarry stool

• Abdominal pain

• Nausea or vomiting especially if it includes blood

• Unexplained fatigue, dizziness, or weight loss

• Shortness of breath or heart palpitations

• Pale skin or cold hands and feet

How It's Diagnosed and Treated

Your healthcare provider may run blood tests, imaging scans, or an endoscopy to identify the source of the bleeding. Treatment depends on the cause:

• Minor cases: May resolve after stopping a medication or making a dietary change.

• More serious conditions: Could require medical procedures, iron therapy, or even blood transfusions if significant blood loss has occurred.

The Bottom Line

Noticing black poop once in a while doesn’t automatically mean something’s wrong. Still, it’s a sign worth paying attention to especially if it’s accompanied by other symptoms. When in doubt, check in with your provider. Your digestive system has a way of sending signals, and color changes are one of the easiest to spot.

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