Yellow stools mixed with black may be caused by dietary factors, medication factors or upper gastrointestinal bleeding. 1. Dietary factors: If you eat animal offal or chicken and duck blood, mixed with other food formed by yellow stools can appear yellow stools mixed with black, this situation is normal, do not need treatment. 2. Drugs: If you have recently taken certain drugs such as bismuth potassium citrate and ferrous sulfate, etc., there may be yellow stools mixed with black, which will disappear after stopping the drugs. 3. Upper gastrointestinal bleeding: various causes of upper gastrointestinal bleeding can appear in the yellow stool with black phenomenon, this situation is recommended to go to the hospital in time to find out the location of the bleeding and give appropriate treatment. There are many other reasons for yellow stools mixed with black, and it is recommended to actively consult the doctor, improve the examination, clarify the cause of the disease, and symptomatic treatment.