Why Is My Poop Black? When to Get Urgent Medical Help
A practical guide to black stool, iron and bismuth, black tarry stool, possible GI bleeding, urgent warning signs, and what to track.
6 mins read
Black stool can sometimes be explained by a food, supplement, or medicine. But black stool that is tarry, sticky, or unusually foul-smelling can be a sign of bleeding higher in the digestive tract and needs urgent medical attention.
Because it can be hard to tell the difference at home, do not ignore a new black stool—especially if there is no clear, temporary explanation or you also feel unwell.
Seek urgent medical care now for black, tarry stool with dizziness, fainting, weakness, shortness of breath, severe abdominal pain, vomiting blood, or vomit that looks like coffee grounds. These can be signs of gastrointestinal bleeding.
Black Stool Is Not Always the Same as Tarry Stool
Some things can darken stool without bleeding. Iron supplements, medicines containing bismuth subsalicylate, activated charcoal, black licorice, blueberries, and blood sausage are examples. If you recently used one of these, it may explain a short-term color change.
Still, a medical professional may need to check the stool for blood if there is any doubt. Black stool caused by digested blood is often described as tarry: very dark, sticky, and sometimes foul-smelling. It can result from bleeding in the esophagus, stomach, or first part of the small intestine.
Do not assume that a supplement or medicine explains the change if the stool is tarry or you have warning symptoms. Do not stop a prescribed medicine without advice from the clinician who prescribed it.
What Can Cause Stool to Look Black?
Black stool can have harmless explanations, but it can also be related to gastrointestinal bleeding. A clinician needs to assess the context rather than diagnose it from color alone.
- Iron supplements. Iron commonly makes stool darker or black.
- Bismuth-containing medicines. Some upset-stomach or diarrhea products can temporarily turn stool black.
- Foods and charcoal. Black licorice, blueberries, blood sausage, and activated charcoal can darken stool.
- Bleeding in the upper digestive tract. Bleeding from the esophagus, stomach, or upper small intestine can produce black, tarry stool. There are many possible causes, which require medical evaluation.
Medicines that increase bleeding risk, such as blood thinners, antiplatelet medicines, aspirin, ibuprofen, or naproxen, are important context to share with a clinician. Do not change or stop them on your own.
What to Track While You Get Advice
Tracking is not a substitute for urgent care. If you have black tarry stool or warning signs, seek help first. For a non-urgent color change with a clear possible explanation, a short record can make a follow-up conversation more useful:
- When it started. Log the date, time, and number of dark stools.
- Appearance. Note whether stool was simply dark or truly black, tarry, sticky, or unusually foul-smelling.
- Recent foods, supplements, and medicines. Include iron, bismuth products, charcoal, pain relievers, blood thinners, alcohol, and new medicines or dose changes.
- Other symptoms. Record abdominal pain, nausea, vomiting, dizziness, fainting, weakness, shortness of breath, fever, and red blood in stool or vomit.
- Relevant history. If you know you have ulcers, liver disease, previous gastrointestinal bleeding, or a recent stomach illness, mention this to a healthcare professional.
SimplePoo provides a private way to log bowel movement dates and brief notes, review regularity, and export a CSV or PDF if a healthcare professional asks for your history.
When to Seek Urgent Help
Seek emergency medical care immediately if black, tarry stool appears with any signs that you may be losing blood or becoming seriously unwell:
- Dizziness, fainting, confusion, unusual weakness, pale skin, a fast heartbeat, or shortness of breath
- Vomiting blood or vomit that looks like coffee grounds
- Severe, sudden, or worsening abdominal pain
- Black tarry stool together with red blood in stool
- Black stool while taking blood-thinning medicine, especially if the change is new or unexplained
Contact a healthcare professional promptly for any new black stool when you are unsure of the cause, even without the symptoms above. They can decide whether you need examination, blood tests, stool testing, or other evaluation.
Bottom Line
Iron, bismuth, charcoal, and some dark foods can make stool look black. However, black, tarry, sticky, or foul-smelling stool can indicate bleeding in the digestive tract and should be treated as urgent—especially when it comes with dizziness, weakness, pain, or vomiting blood.
Record relevant food, medicine, and symptom details if it is safe to do so, but do not wait to seek help for a possible bleeding warning sign.