Brief Answer:
Bleeding in upper GI tract vs eating something that colors stool.

Detailed Answer:
Hello and welcome,

Unless a person is taking a medication or product that is known to makes stools look black, such as Pepto Bismol (bismuth), black stools are considered concerning because it can mean there is bleeding from the stomach or esophagus.

When there is bleed in the stomach (from he stomach or esophagus), the stomach acid acts on it making the stool look black and tarry. If there is vomiting, the blood looks like coffee grounds.

Substances that color the stool black but are not concerning (not a sign of bleeding) are bismuth, blueberries, charcoal, iron tablets, and licorice.

If you are having black, tarry stool, it is best for you to go in to be seen to make sure this is not from blood as described above.

I hope this information helps. Please let me know if I can provide further information.

---