Is it normal for stool to always be black?

Black stool may be a normal phenomenon or could indicate an abnormal condition, depending on the specific cause. Common causes include consumption of certain foods or medications, or gastrointestinal bleeding.

1. Consumption of certain foods

Eating large amounts of leafy green vegetables, animal organs, or animal blood products can cause stool to appear black. This is considered a normal occurrence, and stool color typically returns to normal after stopping consumption of these foods.

2. Medications

Medications used for eradicating Helicobacter pylori or iron supplementation—such as colloidal bismuth pectin dry suspension or ferrous succinate tablets—can lead to persistently black stools. This occurs when iron in the medication reacts with hydrogen sulfide in the gut. This is also a normal phenomenon, and stool color usually returns to normal after discontinuing the medication.

3. Gastrointestinal bleeding

If black stool is present in large amounts, appears tarry, or has a foul, fishy odor, especially when accompanied by symptoms such as abdominal pain or chest tightness, this may indicate an abnormal condition. It is recommended to seek medical evaluation at a hospital, including tests such as gastroscopy, to determine whether gastrointestinal bleeding is occurring.