Why is it black and yellow?

The reasons for black stool after yellow include dietary factors, drug factors, gastrointestinal bleeding, etc.

1. Dietary factors

If a large number of pork liver, duck blood and other foods are eaten in a short period of time, it may affect the color of stool, resulting in black stool after yellow stool.

2. Drug factors

If the patient takes iron, bismuth and other drugs, the drugs will produce black substances in the metabolic process in the body, causing black stool after yellow stool.

3. Gastrointestinal bleeding

When suffering from gastric ulcer, gastric cancer and other diseases, it may lead to gastrointestinal bleeding. Due to the oxidation of trivalent iron ions in the blood into divalent iron ions in the digestive tract, it will cause black stool after yellow stool.