Noticing that your poop is black can be an unsettling experience. It’s a sudden change that can cause immediate concern and often leads people to search online for answers.
Many people have this concern at some point, and it’s important to know what might cause it, when it’s normal & when you should see a doctor.
This blog provides an in-depth explanation of everything you need to know about black stool.
What Is Black Poop?
Sometimes your stool can be very dark, almost black, and feel sticky. This can happen for a few reasons. Maybe you changed your diet, started a new medicine, or it could be a medical issue you shouldn’t ignore.
Poop naturally comes in different colours like brown, yellowish, or even green. That mostly depends on what you eat, what medicines you’re taking, and how much bile (a greenish fluid that helps with digestion) is in your system.
But when your poop turns black or bright red, it could be a sign of bleeding inside your body. So even if you think you know what’s causing it, it’s always a good idea to check with your doctor.
Want to know if your stool type is normal or a sign to see a doctor? Download Bristol Stool Chart (PDF) and track your bowel health
What is Melena?
Melena is the medical term for black, tar-like stool caused by digested blood in your gastrointestinal (GI) tract. It usually means there’s bleeding somewhere in the upper part of your digestive system, like your oesophagus, stomach, or the first part of your small intestine.
Here’s what actually happens:
- Blood from the upper GI tract mixes with stomach acid and digestive enzymes.
- As it travels through your intestines, it gets broken down.
- By the time it comes out, it’s black, sticky, and smells really bad, that’s melena.
Causes of Black or Tarry Stool (Poop)
Black stool can occur for various reasons. Some causes are harmless, while others can be serious. The colour change comes from what you eat, what medicines you take, or internal bleeding.
Non-serious causes:
- Iron supplements
- Bismuth medications (like Pepto-Bismol)
- Dark foods: black liquorice, blueberries, beets, dark chocolate, grape juice
- Activated charcoal (used in poisoning or detox products)
These usually don’t come with pain or other symptoms, and the stool returns to normal when you stop the food or drug causing it.
More serious causes:
- Bleeding ulcers (in the stomach or small intestine)
- Gastritis (inflamed stomach lining) or oesophagitis
- Oesophageal tears or varices
- Certain cancers (oesophagus, stomach, pancreas)
- Heavy NSAID use (like ibuprofen or aspirin)
- Viral haemorrhagic fevers (rare but possible)
- Mallory-Weiss tears (from severe vomiting)
- Upper GI cancers
- NSAID overuse
- H. pylori infection (linked to ulcers)
How Can I Tell If My Black Stool Is Melena?
If you notice black stool and aren’t sure what’s causing it, a doctor can run a stool test to check for hidden blood.
What does it look like?
Melena is usually jet black, shiny, and sticky, almost like tar. That distinct texture can help set it apart from stool that turns black because of food or supplements. In some cases, especially if there’s diarrhoea, it might be looser or more dark brown than black. A small amount of bleeding might not look dramatic, but it can still be serious.
What does it smell like?
Melena has a very strong, unpleasant smell. That odour comes from blood breaking down as it moves through your digestive system. The longer it’s in there, the darker and smellier it gets. Black stool from harmless causes like iron pills or dark foods usually doesn’t have that same foul odour.
If your black stool is also sticky, tar-like, and foul-smelling, it’s more likely to be melena, which means you should get checked out.
Symptoms of Black Poop
These symptoms can help you understand what is causing the bleeding and where it is happening. Here’s what to look out for:
- Stomach pain can indicate a problem such as an ulcer, inflammation (gastritis), or irritation caused by medication or alcohol (gastropathy).
- Chest pain may indicate bleeding in the oesophagus.
- Pain in the upper belly or back could be related to a pancreatic issue.
- No pain at all might still mean something serious, like a silent ulcer, a tumour, or a burst blood vessel.
Some people also have vomiting along with upper GI bleeding:
- If you vomit bright red blood, it usually means there’s active bleeding in the stomach or oesophagus.
- If the vomit looks dark and grainy, like coffee grounds, it means the blood has been sitting in the stomach for a while, and the bleeding may have slowed or stopped.
Common Foods That Cause Black Stool
Sometimes, what you eat is all it takes to change the colour of your stool. Certain dark-coloured foods and drinks can make your poop look black, but it’s usually nothing to worry about. Some of the common ones include:
- Blueberries
- Dark chocolate cookies (like Oreos)
- Beets
- Black liquorice
- Grape juice
- Dark leafy greens like kale or spinach
- Blood sausage
- Foods or drinks with artificial colourings
- Dark beer
If your black stool is from food, the colour should go back to normal once you stop eating or drinking the thing that caused it.
Can Iron Supplements Cause Black Stool?
Yes, iron supplements can make your poop look black or very dark green. This is a common side effect when you’re taking iron to treat anaemia, a condition where your body doesn’t have enough red blood cells to carry oxygen properly.
This colour change isn’t harmful on its own, but you should call your doctor if:
- Your stool looks black and tar-like, which could signal bleeding.
- You see red streaks or blood in your poop.
How Bismuth-Based Medicines Lead to Black Stool?
Medicines that contain bismuth subsalicylate, like Pepto-Bismol, are often used to treat things like diarrhoea, heartburn, or an upset stomach. They work by calming inflammation in your gut and slowing down fluid loss.
When bismuth mixes with sulphur in your saliva and digestive system, it forms a dark substance called bismuth sulphide. That’s what turns your stool black.
It’s not dangerous, and the colour will likely return to normal within a few days after you stop taking the medication.
How do Tumours Cause Bleeding and Black Stool?
Tumours in the digestive tract, whether cancerous or not, can cause internal bleeding. When this blood moves through the gut, it mixes with digestive fluids, turns dark, and gives stool a black, tar-like appearance.
Tumours in the upper digestive tract, such as the oesophagus, stomach, or small intestine, are more likely to cause this because the blood has more time to be digested. The bleeding happens when tumours damage the lining of the digestive system.
While tumours can be a cause, black stool can also come from ulcers, medications, or other health issues. It’s important to see a doctor if you’re unsure what’s causing it.
What Black Flecks in Poop Might Mean?
If you see black specks or spots in your stool instead of the whole thing being dark, it could be from undigested food, such as pieces of blueberries or black beans.
But these black flecks can also be linked to the same things that cause fully black stool. This includes eating dark-coloured foods, taking certain medications, or bleeding somewhere in your digestive system. If the stool looks dark brown and has a gritty or coffee ground-like texture, it might be a sign of old blood. That could point to bleeding higher up in your digestive tract.
When Is Black Poop Normal?
Black poop is normal when it is the result of something you ate or a supplement you’re taking. Here are a few normal causes:
- Iron supplements.
- Bismuth-based medications like Pepto-Bismol.
- Dark-coloured foods such as black liquorice, blueberries, beets, or dark chocolate.
- Foods or drinks with artificial colouring
In these cases, the stool may look dark but won’t have a tar-like texture or a foul smell. The colour usually goes back to normal once you stop eating or taking whatever caused it. If you’re not having any pain, nausea, or other symptoms, and you can link the change to food or medication, it’s likely nothing serious.
Diagnosis for Black Stools
If your doctor suspects something more than just food or supplements is behind the black stool, they may recommend one or more of these tests:
- Stool test: Checks for hidden (occult) blood in your stool that you might not see yourself.
- Endoscopy: A thin, flexible tube with a camera is inserted through your mouth to examine your oesophagus, stomach, and upper part of the small intestine. Used when bleeding is suspected in the upper digestive tract.
- Colonoscopy: Similar to an endoscopy, but the camera goes in through the rectum to look at your colon and lower digestive tract. This helps find bleeding lower in the system.
- Blood tests: Look for signs of anaemia (low red blood cell count), which can happen if you’ve lost blood over time.
- CT scan: Provides detailed images of your abdomen to spot possible sources of bleeding or other issues.
- Angiography: A special type of imaging that shows blood flow in your vessels. It can help pinpoint exactly where the bleeding is happening.
How to Treat Black Poop (Melena)?
Melena isn’t a disease; it’s a symptom of something else going on in your digestive system. So the focus isn’t on treating the black stool itself, but on fixing whatever’s causing the bleeding.
If the Cause Is Not Serious
- Food-related: If dark foods like liquorice, blueberries, or beets are the reason, the stool usually returns to its normal colour in a day or two once you stop eating them.
- Medications or supplements: Iron pills or medications like Pepto-Bismol can darken stool. The colour typically goes back to normal after you stop taking them. But don’t stop prescribed medicines without talking to your doctor first.
If It’s Melena (Due to Internal Bleeding)
When black stool is caused by actual bleeding in the digestive tract, treatment depends on the condition behind it. Here’s how different causes are usually handled:
- Gastritis: Treated with acid-reducing medications like antacids or proton pump inhibitors. If it’s caused by an H. pylori infection, antibiotics are added.
- Bleeding ulcers: Doctors may use an endoscopy to seal the ulcer. If that doesn’t work, they might use a procedure to block the bleeding vessel or do surgery. Antibiotics are given if H. pylori is the trigger.
- Oesophagitis: Acid reflux-related cases are managed with antacids and lifestyle changes, like avoiding spicy food. Infections are treated with antibiotics. Serious cases may need surgery.
- Oesophageal varices: These swollen veins can rupture and bleed heavily. Doctors may tie them off with bands or use medications to reduce pressure and prevent more bleeding.
- Mallory-Weiss tears: Minor tears often heal on their own. Severe bleeding may need an endoscopy to stop it using clips or cauterisation. Avoiding alcohol helps prevent future tears.
- Upper GI cancers: Treatment depends on the type and stage of the cancer. Options may include surgery, chemotherapy, radiation, or targeted drug therapy.
When Should You Worry About Black Stool?
Get medical help immediately if you also have:
- Dizziness or lightheadedness
- Weakness or fainting
- Vomiting blood or something that looks like coffee grounds
- Severe or ongoing stomach pain
- Blood in your vomit or red streaks in your stool
- Shortness of breath
- Unexplained weight loss or loss of appetite
- Black stool that lasts more than a couple of days
- Black poop that’s thick, sticky, and has a strong, foul smell
Final Thoughts
Black poop doesn’t always mean danger. It may be due to something you ate or a supplement you’re taking. But if it looks like tar, smells weird, or comes with other symptoms, it could be a sign of bleeding.
Don’t ignore your poop. It’s your body’s way of showing you what’s happening inside. Pay attention, and when in doubt, talk to a doctor.
Frequently Asked Questions
1. What does blood in poop mean?
It usually means there’s bleeding somewhere in your digestive system. It might look bright red or very dark and tar-like. Either way, call your doctor.
2. What causes bloating and black poop?
It could be something serious, like a bleeding ulcer or even cancer. If you have black poop with bloating or stomach pain, see a doctor right away.
3. Can dehydration cause black poop?
Not usually. Dehydration can make your poop hard and darker brown, but true black stool, especially if it’s sticky or tar-like, can mean bleeding in your gut.
4. What does unhealthy poop look like?
Everyone’s different, but big changes in colour, texture, shape, or how often you go can be a sign that something’s off. Black or bloody poop is always worth checking out with a doctor.
