Why Is My Poop Black? 4 Possible Causes

Let’s address the awkward mystery in the bathroom: black poop. It can be totally harmless (your dinner is a drama queen),
or it can be your body waving a bright red flag… in a surprisingly dark color.

Here’s the big idea: black stool happens for two main reasons:
(1) something stained it (food, supplements, meds), or (2) there’s blood that’s been digested on the way through your upper digestive tract
(often called melena). The difference matters.

Black stool vs. “melena”: what’s the difference?

Not all dark poop is created equal. Stained-black poop is usually from something you ate or took. It often looks dark but not
especially sticky or tarry, and you typically feel fine.

Melena is the medical term for black, tarry stool caused by bleedingusually from the upper GI tract (esophagus, stomach,
or the first part of the small intestine). Blood turns black after it’s exposed to stomach acid and digestive enzymes.

4 possible causes of black poop

Below are the most common explanations doctors see in real life. The first three are often benign. The fourth is the one you never want to shrug off.

1) Iron supplements (and some multivitamins)

If you recently started iron supplementsor even a multivitamin with a decent iron dosecongratulations: your poop may have
joined the goth club.

Iron can darken stool to a deep greenish-black or black. This is a well-known side effect and, by itself, isn’t usually dangerous.
People often notice it after starting iron for anemia, heavy periods, pregnancy/prenatal vitamins, or low iron on lab work.

Clues it’s iron:

• You started iron tablets, liquid iron, or a prenatal vitamin recently.
• You feel mostly fine, aside from possible constipation or mild stomach upset.
• The timing matches: the color change appears within a day or two of starting.

What to do:

• Don’t stop prescribed iron without asking your clinicianespecially if it’s treating anemia.
• If constipation or nausea is rough, ask about dose timing, taking it with food, or switching formulations.
• If you also have severe stomach pain, dizziness, or other red-flag symptoms, get checked. (Iron isn’t a free pass.)

2) Bismuth medicines (like Pepto-Bismol)

Over-the-counter products containing bismuth subsalicylate (famously Pepto-Bismol, and some similar brands)
can turn stool black. It’s common and usually harmless.

The dark color is a chemical reaction that can occur in the digestive tract. It may show up after just a dose or two and usually goes away
within a few days after you stop taking it.

Clues it’s bismuth:

• You took it for nausea, diarrhea, heartburn, or “my stomach hates me today.”
• The stool is darker, but you don’t have bleeding symptoms (like dizziness or faintness).
• The change is short-lived and improves after stopping the medication.

What to do:

• Check the active ingredient label for “bismuth subsalicylate.”
• If you’re on blood thinners, have ulcers, or are prone to GI bleeding, ask a clinician before using it.
• If black stool continues after stopping itor you have red flagsget evaluated.

3) Dark foods, drinks, or food coloring

Sometimes the answer is simply: your diet has range. Dark foods can tint poop black or near-black, especially if you ate a lot of them
or your digestion is moving quickly.

Common food culprits:

• Black licorice
• Blueberries (especially large amounts)
• Dark chocolate, dark cookies, or very dark frosting
• Foods with deep dyes (black icing, colored drinks, certain candies)
• Sometimes beets can cause dark or reddish stool that looks alarming under bad lighting

Clues it’s food:

• You can point to a “dark-food event” in the past 24–48 hours.
• You feel fine otherwise.
• The stool color returns to normal once that food is out of your system.

What to do:

• Give it a day or two and see if it resolves.
• If it doesn’t improve, or you’re unsure, it’s reasonable to call your healthcare provider for guidance.

4) Upper GI bleeding (melena)

This is the serious one. Melena is black, tarry stool caused by bleedingmost often from the upper digestive tract.
The blood turns black as it’s digested.

Upper GI bleeding can happen for several reasons, including:

• Peptic ulcers (often linked to H. pylori infection or frequent NSAID use like ibuprofen/naproxen)
• Gastritis or inflammation/irritation of the stomach lining
• Esophagitis or irritation of the esophagus
• Varices (enlarged veins in the esophagus/stomach, usually tied to serious liver disease)
• Tears in the esophagus after forceful vomiting
• Less commonly, bleeding from tumors or vascular malformations

Red-flag symptoms that need urgent care:

• Black, tarry stool with dizziness, fainting, weakness, or shortness of breath
• Rapid heartbeat or feeling like you might pass out when standing
• Severe belly pain or worsening pain
• Vomiting blood or vomiting material that looks like coffee grounds
• Black stool that appears suddenly with no clear food/medication explanation

Even if symptoms feel “mild,” bleeding can become dangerous quickly. If you suspect bleeding, get evaluated right away.
In the U.S., that usually means the ER or urgent evaluationcall 911 (or your local emergency number) if symptoms are severe.

How clinicians figure out what’s going on

When you report black stool, a good clinician usually starts with the basics: your recent diet, medications/supplements (especially iron, bismuth,
aspirin/NSAIDs, blood thinners), and any other symptoms.

Common tests and next steps

• Stool test for blood (because iron and bismuth can mimic bleeding)
• Blood work (to check anemia and signs of blood loss)
• Endoscopy if upper GI bleeding is suspected (a camera exam of the esophagus and stomach)
• Sometimes imaging or additional tests depending on risk factors and symptoms

The goal is to separate harmless staining from true bleedingand, if it’s bleeding, to find the source and treat it.

What not to do (aka: the “please don’t Google yourself into chaos” section)

• Don’t ignore persistent black stool just because you feel busy or embarrassed.
• Don’t keep taking NSAIDs (like ibuprofen) for stomach pain without guidancethese can worsen ulcers/bleeding.
• Don’t self-diagnose bleeding purely by colordark foods and meds can mimic it, and bleeding can sometimes look different.
• Don’t stop prescribed meds (like iron or blood thinners) without medical advicecall your clinician for a plan.

FAQ: Quick answers to common questions

How long can poop stay black from iron or Pepto-Bismol?

Often a few days, sometimes longer with continued use. If you stop the trigger and black poop persists or you feel unwell, get checked.

Can dehydration cause black poop?

Dehydration can make stool harder and darker, but true black, tarry stool raises concern for melena or staining from foods/meds.
If it’s genuinely black and unexplained, don’t chalk it up to “not enough water.”

What if it’s just one black stool?

A single episode after dark foods or certain medications is often benign. But if there’s no clear explanationor there are red flagsseek medical advice.

When should I see a doctor for black stool?

If it’s unexplained, persistent, or paired with symptoms like dizziness, weakness, fainting, vomiting blood, or significant abdominal pain,
you should be evaluated urgently.

Conclusion

If you’re wondering, “Why is my poop black?” the most common answers are also the least dramatic:
iron supplements, bismuth medicines, or dark foods. But the fourth possibilityupper GI bleeding (melena)is the reason
black stool deserves respect.

If there’s a clear cause and you feel fine, it’s reasonable to monitor for a day or two. If there’s no obvious explanation, the color persists,
or you have any red-flag symptoms, get medical care promptly. Your bathroom deserves peace, not plot twists.

Experience Corner: What people commonly notice (and what they do next)

People rarely wake up thinking, “Today I will investigate stool color.” It usually happens the moment you glance down, pause, and your brain hits the
panic button. Here are a few real-world style scenarios (composites based on common patterns clinicians hear) that show how black stool can play out
and why context matters.

Experience #1: “I started iron and thought I was dying.”

A lot of people begin iron supplements because of anemia or low ferritin and don’t get warned about the color change. Two days later, they see very dark
stool and assume the worst. In many cases, they also notice constipationanother classic iron side effectso the whole situation feels like a prank.
When they connect the timing (new iron + new poop color), the anxiety eases. The best move is usually to message a healthcare provider to confirm it’s
expected and ask about strategies for side effects (like adjusting timing, taking it with food if approved, or choosing a different formulation).

Experience #2: “Pepto-Bismol fixed my stomach… then gave me spooky poop.”

Another common story: someone takes bismuth subsalicylate for a stomach bug or heartburn. Symptoms improve, life is gooduntil the next bathroom trip
looks like it belongs in a Halloween movie. Because the color change can happen quickly, it’s easy to blame a serious illness instead of the medication.
Often, stopping the product leads to stool color returning to normal in a few days. But people who are on blood thinners, have ulcer history, or develop
additional symptoms should get medical guidance rather than guessing.

Experience #3: “It was the food. It was absolutely the food.”

Sometimes it’s just a “dark food weekend”: black licorice, blueberries, dark chocolate cake, maybe a charcoal-colored drink or candy. The stool looks
darker for a day or two, and then everything returns to normal once digestion catches up. People often learn a practical lesson: if you’re ever unsure,
the best question is, “What did I take or eat in the last 48 hours?” Keeping a quick mental log can prevent unnecessary panic (and unnecessary internet
rabbit holes).

Experience #4: “I tried to ignore it, but the symptoms convinced me.”

The more concerning experiences usually include more than color. People describe feeling unusually weak, dizzy when standing, or short of breath. Some
notice stomach pain that’s new or worsening. In those cases, black stool can be a clue pointing toward upper GI bleeding, and the right decision is to
seek urgent evaluation. Many people feel embarrassed and delay careuntil symptoms become too loud to ignore. The takeaway is simple: medical teams have
heard it all, and “black stool” is a normal, important symptom to report. Getting checked can be the difference between a quick treatment and a bigger
emergency.

If there’s one consistent theme in these experiences, it’s this: context is everything. Medications and foods can explain black poop,
but persistent or unexplained black stoolespecially with red-flag symptomsshould be treated as a medical priority.