Medically Reviewed By: Mark Aquino, NP – Urgent Care Nurse Practitioner, author of Physical Assessment for Nurses Simplified. This article is based on real-world urgent care experience and current clinical guidelines.
Black stool after Pepto-Bismol is often a harmless, temporary side effect. Pepto-Bismol contains bismuth subsalicylate, which can darken the stool and sometimes the tongue. The color change usually goes away within a few days after the medicine is stopped. [1]
However, not every black stool is caused by Pepto-Bismol. Stool that is truly black, sticky, tar-like, or unusually foul-smelling can be a sign of bleeding higher in the digestive tract. Because gastrointestinal bleeding can become serious, it is important not to assume that a black stool is harmless if you feel unwell, have warning signs, or are not sure what you are seeing. [2][3]
Why Pepto-Bismol can turn stool black
Bismuth subsalicylate is used for short-term relief of diarrhea, upset stomach, heartburn, indigestion, nausea, and gas. A temporary darkening of the stool or tongue is a known and generally harmless effect of medicines containing bismuth, including Pepto-Bismol. [1][2]
The color change may appear dark brown, greenish-black, or black. It can happen after taking the medicine for a short time and may continue briefly after you stop it. By itself, a change in stool color does not necessarily mean there is blood in the stool. [1]
Still, Pepto-Bismol is not appropriate for everyone. Its label advises against use in people who have an ulcer, a bleeding problem, or bloody or black stool that was present before taking the medicine. It also contains a salicylate, a medicine related to aspirin. [2]
How can you tell harmless dark stool from black tarry stool?
It is not always possible to tell at home. Stool color can vary with food, medicines, and digestion, and a clinician can test a stool sample for blood when needed. [3]
These features may help you decide how quickly to seek care, but they cannot diagnose the cause.
Features more consistent with a Pepto-Bismol color change
- You took Pepto-Bismol or another bismuth-containing medicine shortly before the color change.
- The stool is dark but otherwise has a usual stool-like appearance and consistency.
- You feel generally well and do not have faintness, weakness, severe stomach pain, or vomiting.
- The dark color improves within several days of stopping the medicine. [1]
Features that may suggest bleeding
Black, tarry stool caused by digested blood is called melena. It is often described as jet-black, shiny or sticky, and unusually strong-smelling. It may occur with weakness, dizziness, shortness of breath, abdominal pain, or vomiting blood or material that resembles coffee grounds. [3][4]
Do not rely on appearance alone if you are concerned. A person can have gastrointestinal bleeding without severe pain, and some people have few symptoms at first. [4]
When to call 911 or go to the emergency department
Call 911 or have someone take you to the emergency department now if you have black or tarry stool along with any sign that bleeding may be severe or that your body is not getting enough blood.
- Fainting, near-fainting, new confusion, or extreme weakness
- Dizziness or lightheadedness, especially when standing
- Rapid heartbeat, pale or clammy skin, cold hands or feet, or trouble staying awake
- Vomiting bright red blood or vomit that looks like coffee grounds
- Severe, sudden, or worsening abdominal pain
- Chest pain, shortness of breath, or trouble breathing
- A large amount of blood from the rectum
These can be signs of significant gastrointestinal bleeding or shock, which is life-threatening. Do not drive yourself if you feel faint, weak, confused, or severely ill. [4][5]
When urgent care or same-day medical advice is appropriate
Contact a clinician promptly, use urgent care, or seek same-day medical advice if any of the following apply:
- You have black stool and are not certain it is related to Pepto-Bismol.
- The stool looks tarry, sticky, or has a very strong unusual odor.
- Dark stool continues after you have stopped Pepto-Bismol for several days.
- You have recurring black stools, even if you feel fairly well.
- You have upper abdominal burning or pain, nausea, vomiting, poor appetite, or unexplained fatigue.
- You take a blood thinner, antiplatelet medicine, daily aspirin, or frequent anti-inflammatory pain medicine.
- You have a history of an ulcer, gastrointestinal bleeding, liver disease, or a bleeding disorder.
- You are pregnant, age 65 or older, have a weakened immune system, or have other significant medical conditions and are having diarrhea or vomiting. [1][3][4][6]
Urgent care can be reasonable for a stable person who needs an examination or guidance but does not have emergency symptoms. Keep in mind that urgent care centers vary in their ability to do blood tests, imaging, or urgent endoscopy. If bleeding is suspected, the clinician may direct you to an emergency department for further evaluation.
Common causes of black stool besides Pepto-Bismol
Some foods, supplements, and medicines can darken stool without causing bleeding. Examples include iron supplements, activated charcoal, black licorice, and blueberries. [3]
But black stool may also result from bleeding in the esophagus, stomach, or upper small intestine. Common causes of upper gastrointestinal bleeding include ulcers, inflammation of the stomach lining, inflammation or tears in the esophagus, and enlarged veins in the esophagus or stomach in people with advanced liver disease. [4]
Peptic ulcers are sores in the lining of the stomach or first part of the small intestine. The two most common causes are infection with Helicobacter pylori bacteria and use of nonsteroidal anti-inflammatory drugs, often called NSAIDs. NSAIDs include ibuprofen, naproxen, and aspirin. [5]
Taking an NSAID does not mean you will have an ulcer or bleeding. However, risk can be higher with regular or high-dose use, a past ulcer, older age, alcohol use, certain other medicines, or use of blood thinners. Do not stop a prescribed blood thinner or aspirin on your own because of stool color; seek medical advice promptly instead. [4][6]
Should you stop taking Pepto-Bismol?
If you notice dark stool after taking Pepto-Bismol and otherwise feel well, stop taking additional doses for the moment and review the package directions. The dark color should be temporary. [1][2]
Do not keep taking Pepto-Bismol to treat ongoing symptoms if you have warning signs. The product label says to ask a doctor before use if you have fever or mucus in the stool, and not to use it if you have an ulcer, a bleeding problem, or bloody or black stool. It also advises stopping use and contacting a doctor if diarrhea lasts longer than 2 days or symptoms worsen. [2]
Seek advice from a pharmacist or clinician before using bismuth subsalicylate if you take warfarin or another blood thinner, daily aspirin, or medicines for diabetes, arthritis, or gout. Drug interactions and individual health conditions can affect whether it is safe for you. [1]
Important precautions for children and teenagers
Children and teenagers who have chickenpox or flu-like symptoms should not use Pepto-Bismol unless a doctor says it is appropriate. Because the medicine contains a salicylate, the label warns about the rare but serious risk of Reye’s syndrome in this situation. [2]
For an infant, young child, or teenager with diarrhea, vomiting, dehydration, unusual sleepiness, behavior changes, or black or bloody stool, contact a pediatric clinician promptly. Young children can become dehydrated more quickly than adults. [1][7]
Safe home care for an upset stomach or diarrhea
If you do not have warning signs and your symptoms are mild, focus on preventing dehydration and giving your stomach time to settle.
For more on causes, dehydration signs, and when to seek care, see our guide to diarrhea.
- Take frequent small sips of water, broth, or an oral rehydration drink.
- Eat simple foods as tolerated. You do not need to force food if nausea is limiting your appetite, but try to keep drinking fluids.
- Avoid alcohol while your stomach is upset, especially if you have vomiting, abdominal pain, or possible bleeding.
- Follow the label directions for any over-the-counter medicine. Do not combine products without checking the active ingredients.
- Avoid using ibuprofen or naproxen for stomach pain unless a clinician has told you to use them, because NSAIDs can irritate the stomach and increase gastrointestinal bleeding risk. [4][6]
Adults should contact a clinician right away for diarrhea with black tarry stool, red blood, pus, severe abdominal or rectal pain, frequent vomiting, dehydration symptoms, or high fever. Adults should also seek advice if diarrhea lasts more than 2 days. [7]
What a clinician may check
A clinician will ask when the stool color began, whether you took Pepto-Bismol, iron, aspirin, NSAIDs, blood thinners, or other medicines, and whether you have pain, vomiting, dizziness, or a history of ulcers or bleeding. They may examine your abdomen and check your heart rate and blood pressure. [6]
Depending on your symptoms, evaluation may include a stool test for blood, blood tests to look for anemia or other effects of bleeding, and tests for H. pylori. If gastrointestinal bleeding is suspected, a clinician may recommend an endoscopy, which uses a thin flexible camera to look inside part of the digestive tract. The needed tests depend on your symptoms and how urgent the situation appears. [3][6]
What to remember
Black stool after Pepto-Bismol is commonly a harmless medication effect, especially when it starts after use of the medicine, is not sticky or tar-like, and occurs without other symptoms. Still, black tarry stool can indicate gastrointestinal bleeding.
If you have dizziness, fainting, weakness, vomiting blood, coffee-ground vomit, severe abdominal pain, trouble breathing, or symptoms of shock, call 911 or seek emergency care. If you are unsure whether dark stool is from Pepto-Bismol or blood, it is safer to contact a healthcare professional promptly rather than guessing.
References
- National Library of Medicine. Bismuth subsalicylate: MedlinePlus Drug Information [Internet]. Bethesda (MD): U.S. National Library of Medicine; [cited 2026 Aug 16]. Available from: https://medlineplus.gov/druginfo/meds/a607040.html
- DailyMed. Pepto Bismol caplets: bismuth subsalicylate tablet, drug facts [Internet]. Bethesda (MD): National Library of Medicine; [cited 2026 Aug 16]. Available from: https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=01b318d2-586d-4953-8f98-addc4e3cd441&type=display
- MedlinePlus Medical Encyclopedia. Black or tarry stools [Internet]. Bethesda (MD): U.S. National Library of Medicine; [cited 2026 Aug 16]. Available from: https://medlineplus.gov/ency/article/003130.htm
- National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of GI bleeding [Internet]. Bethesda (MD): National Institutes of Health; [cited 2026 Aug 16]. Available from: https://www.niddk.nih.gov/health-information/digestive-diseases/gastrointestinal-bleeding/symptoms-causes
- National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of peptic ulcers (stomach or duodenal ulcers) [Internet]. Bethesda (MD): National Institutes of Health; [cited 2026 Aug 16]. Available from: https://www.niddk.nih.gov/health-information/digestive-diseases/peptic-ulcers-stomach-ulcers/symptoms-causes
- National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of GI bleeding [Internet]. Bethesda (MD): National Institutes of Health; [cited 2026 Aug 16]. Available from: https://www.niddk.nih.gov/health-information/digestive-diseases/gastrointestinal-bleeding/diagnosis
- National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of diarrhea [Internet]. Bethesda (MD): National Institutes of Health; [cited 2026 Aug 16]. Available from: https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea/symptoms-causes
About the author: Mark Aquino MSN, FNP-C. Mark has a Masters of Science in Nursing from West Coast University and is a board certified family nurse practitioner with over 8 years of real world experience in healthcare and currently practicing in urgent care diagnosing and prescribing treatments in California, USA. He is author of the book Physical Assessment for Nurses Simplified.