It may be related to diet, or it may be caused by medication, in addition to symptoms that may be caused by bleeding in the gastrointestinal tract.
Black stools, also known as tarry stools, are generally common due to the following two causes.
1. Normal physiological conditions caused by diet or medication, such as frequent consumption of pork blood, pork liver, spinach, etc., may cause such symptoms if you are taking iron or medications containing iron, iron-fortified milk powder, rice flour, or nutritional supplements containing iron.
2. If you usually have nausea, vomiting, weight loss, etc., it may be caused by stomach cancer. If you usually have periodic upper abdominal pain and the pain is clearly related to diet, it may be caused by peptic ulcer. If you have been taking NSAIDs for a long time, then black stools may be a result of gastrointestinal bleeding due to drug irritation of the gastric mucosa. In addition, esophagitis, esophageal tumors, acute and chronic gastritis can all cause black stools.
If the symptoms persist for a long time you should go to a gastroenterologist for a gastroscopy to get a clear diagnosis.