Doctors Break Down What’s Behind Your Black Poop
At this point in life, you likely have a good idea of what your average bowel movements look like. So if you happen to notice they’re darker than usual, it’s understandable to wonder, “Why is my poop black?”
If your poop is just black, it could just be something you ate. But if it’s black and tarry, doctors say it’s definitely not something to ignore.
Meet the experts: Ashkan Farhadi, M.D.,a gastroenterologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA; Samuel A. Akinyeye, M.D., assistant professor in the division of gastroenterology, hepatology, and nutrition at The Ohio State University Wexner Medical Center.
Here’s what could be behind your black poop, plus what to do next.
Why is my poop black?
There are a few reasons why you might have black poop. These are the biggest, according to gastroenterologists.
You’re taking iron supplements.
Black poop is a common side effect of iron supplements, which are usually taken for anemia (a condition that happens when you don’t have enough red blood cells in your body).
“Unabsorbed iron can form complexes with compounds in your gastrointestinal tract that can lead to black stools,” says Samuel A. Akinyeye, M.D., assistant professor in the division of gastroenterology, hepatology, and nutrition at The Ohio State University Wexner Medical Center.
If you’re able to get a closer look at your poop, black BMs due to iron will usually have a greenish tint, says Ashkan Farhadi, M.D., a gastroenterologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA.
You ate dark foods.
Dark foods like beets, blueberries, dark licorice, and even a lot of spinach can cause your poop to look black, Dr. Farhadi says. “Dark foods contain certain dyes which can turn the food red or black,” Dr. Akinyeye. But when mixed with the other stuff in your gut, it can cause your poop to look black, he says.
One thing to note, per Dr. Farhadi: This shouldn’t change the consistency of your poop—just the color.
You took bismuth medications.
Bismuth medications are usually used to treat diarrhea, upset stomach, and heartburn, and can include brands like Pepto-Bismol and Kaopectate. But while they can calm your stomach, they also can mess with your poop.
“Bismuth can combine with sulfur that is naturally occurring in your body and lead to stool turning black,” explains Dr. Akinyeye.
You have gastrointestinal bleeding.
This will usually cause your poop to look tarry and black, Dr. Akinyeye says.
“Bleeding from your GI tract, when it comes in contact with digestive enzymes, turns from red to black resulting in those black/tarry stools,” he says. Dr. Akinyeye also says that black poop from gastrointestinal bleeding “has a unique smell that you won’t soon forget.”
“The tarry or stickiness of the stool and the smell are what differentiate true GI bleeding from other causes such as iron supplements, dark foods, and bismuth-containing medications,” he adds.
Gastrointestinal bleeding can be caused by a range of potential health issues, including ulcers, varices (swollen veins in the esophagus), and even cancer.
What should poop look like?
There is a range with what is considered healthy poop. In general, most poop is a brownish color, Dr. Farhadi says. This is due to a mix of things, including bile that breaks down fats passing through your digestive system, bilirubin (a substance that’s created when red blood cells leave your body as a waste product), and the digested remains of the food you ate, according to the Cleveland Clinic.
Shape-wise, you usually want your poop to have some level of form, but not be overly hard or too soft, Dr. Farhadi says. (However, you’ll have variations in shape and color from time to time—that’s normal.)
When to see a doctor for black poop
If your poop is black and you can easily tie it to something you ate or took, doctors generally aren’t concerned. “This should go away when you stop taking the medication or eat something else,” Dr. Farhadi says.
But it’s important to contact a doctor if you see that black, sticky poop. “You should especially be paying attention if you are feeling tired, short of breath, or weak as these can also be associated with gastrointestinal bleeding,” Dr. Akinyeye says.
Your doctor will likely want to give you a physical evaluation and order testing to find out more.
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