Black Stool: What Causes It and What You Need to Know

One of the most common reasons for black stool is internal bleeding. When blood from the upper digestive tract—such as the esophagus, stomach, or duodenum—travels through the intestines, it undergoes chemical changes that cause the stool to appear dark or black. This is often referred to as melena and can be a sign of a serious medical condition.

Common Causes of Black Stool

1. Upper Gastrointestinal Bleeding

When there is bleeding in the upper digestive system—such as from an ulcer, gastritis, or a tear in the esophagus—the blood may turn black as it passes through the digestive tract. This change occurs due to the interaction of digestive enzymes with blood, altering its color and texture.

2. Respiratory Tract Bleeding

Bleeding from the nose (epistaxis) or minor bleeding in the throat or upper respiratory system can sometimes lead to black stool. When blood is swallowed and later expelled through the digestive system, it may appear darker than usual.

3. Diet and Medications

Not all black stools are caused by bleeding. Certain foods and supplements can also lead to dark-colored stools. Consuming animal blood (like pig or duck blood) or taking iron supplements and certain herbal medications—such as those containing Angelica sinensis (Dang Gui)—can darken the stool significantly.

When to Seek Medical Attention

If you suspect bleeding, it's important to determine the source. Lower gastrointestinal bleeding, such as from hemorrhoids or colon issues, typically results in bright red blood in the stool. However, if you experience frequent bowel movements along with symptoms like nausea, abdominal discomfort, or cramping, it's essential to consult a healthcare professional.

Black stool can be alarming, but understanding the potential causes and knowing when to seek help is crucial for your health. Always consult a doctor to rule out serious conditions, especially if symptoms persist or worsen over time.