A 14-year-old girl has passed black stool.

In general, defecation refers to the act of passing stool. If a 14-year-old girl passes black stool, it may be caused by factors such as iron supplementation, dietary influences, or gastrointestinal bleeding. The specific causes are analyzed as follows:

1. Iron intake

If the girl is taking iron-containing medications, such as iron supplements, this may lead to black stool. Iron supplements can alter stool color, turning it black. This symptom usually resolves after discontinuation of the medication.

2. Dietary factors

Certain foods, such as black grapes, dark chocolate, and dark soy sauce, may cause black stool. This condition is typically temporary and generally not a cause for concern.

3. Gastrointestinal bleeding

Gastrointestinal bleeding refers to blood loss within the digestive tract, which may result from conditions such as gastric ulcers, duodenal ulcers, or esophageal varices. Gastrointestinal bleeding can lead to black, tarry stools (melena). Under a doctor's guidance, patients may use medications such as lansoprazole tablets or omeprazole enteric-coated tablets for treatment.

Besides the above common causes, black stool could also be related to hepatitis, liver cirrhosis, or stomach cancer. It is recommended to seek timely medical evaluation at a hospital to determine the underlying cause and receive appropriate treatment. In daily life, it is important to maintain healthy habits and avoid consuming spicy or irritating foods, which may hinder recovery.