Dark poop is usually not a sign of anything dangerous. The most common causes are foods like blueberries and black licorice, iron supplements, and over-the-counter stomach medications like Pepto-Bismol. However, black stool that is tarry, sticky, and has a strong foul smell can signal bleeding in the upper digestive tract, which does need medical attention.
The key is figuring out which type of dark stool you’re dealing with. In most cases, a quick mental inventory of what you’ve eaten or taken in the last day or two gives you the answer.
Common Foods and Supplements That Darken Stool
A surprisingly long list of everyday items can turn your poop dark brown or even jet black. Iron supplements are one of the most frequent culprits, often producing dark green to black stool. Pepto-Bismol does the same thing: its active ingredient reacts with trace amounts of sulfur in your saliva and digestive tract, forming a black compound called bismuth sulfide. Activated charcoal, popular in supplement form, also turns stool very dark.
On the food side, blueberries are a classic offender. Eating a large amount can produce stool so dark it looks black. Black licorice has the same effect, and so does blood sausage. Even handfuls of brightly colored candy can mix together in your gut and produce black-looking stool. Beets, for their part, create a deep red that people sometimes mistake for blood.
If any of these sound familiar, your dark stool is almost certainly harmless. Once you stop eating the food or taking the supplement, the color should return to its usual brown within a couple of days as the staining substance clears your system.
When Dark Stool Signals Bleeding
The type of dark stool that does warrant concern is called melena. It looks and feels different from food-stained poop in several distinct ways. Melena is jet black with a tarry, sticky consistency, almost like roofing tar. It also has a particularly strong, offensive odor that’s noticeably worse than normal stool. That smell comes from blood being broken down and digested as it travels through your intestines.
Melena indicates bleeding somewhere in your upper digestive tract: the esophagus, stomach, or the first section of the small intestine. When blood sits in the gut long enough to be partially digested by stomach acid, the red hemoglobin in blood gets chemically converted into a dark brown or black substance. The longer the blood has traveled through your system, the darker and more foul-smelling the stool becomes. A small amount of bleeding may look more dark brown than fully black.
Common causes of upper GI bleeding include stomach ulcers, inflammation of the stomach lining, and enlarged veins in the esophagus. These are treatable conditions, but they do require medical evaluation.
How to Tell the Difference
The practical way to sort this out starts with three questions. First, have you recently eaten blueberries, black licorice, beets, or other deeply pigmented foods? Second, are you taking iron supplements, Pepto-Bismol, or activated charcoal? Third, what does the stool actually look like and smell like?
Food-stained stool is dark but typically has a normal consistency and doesn’t smell dramatically worse than usual. Melena, by contrast, is sticky and tar-like with a distinctly foul odor you’d recognize as unusual. If you can’t identify an obvious dietary cause and the stool has that tarry, sticky quality, it’s worth getting checked.
Your doctor can run a simple stool test called a fecal occult blood test to check for hidden blood. The newer version of this test, called a fecal immunochemical test (FIT), specifically detects human blood and tends to produce fewer false results than the older version. Either test can quickly confirm whether blood is present.
Symptoms That Suggest Something More Serious
Dark stool on its own, without other symptoms, is less alarming than dark stool accompanied by other signs. Pay attention if you also experience lightheadedness or dizziness, which can indicate enough blood loss to affect your circulation. Abdominal pain, vomiting (especially if the vomit looks like dark coffee grounds), unusual fatigue, or feeling faint are all signals that bleeding may be significant.
If your dark stool comes with any of these symptoms, or if it persists for more than a couple of days after you’ve stopped any suspect foods or supplements, seek medical attention promptly rather than waiting it out.
Dark Stool in Newborns
If you’re a new parent searching this, there’s good news: a newborn’s first poop is supposed to be dark. Meconium, as it’s called, is thick, sticky, and nearly black. Babies typically pass it within 24 to 48 hours after birth. Over the following days, as the baby starts drinking breast milk or formula, stool gradually transitions to a lighter color and softer texture.
The concern with newborns is actually the opposite: if a baby doesn’t pass meconium within 48 hours, it could indicate a blockage or other condition that needs evaluation. Once that first dark stool has passed and the color starts shifting, the digestive system is working as expected.