Dark and slimy stools may be tarry black stools, and gastrointestinal bleeding may be present if there has been no recent consumption of iron-containing foods or medications. 1. Iron-containing foods such as spinach, duck blood, etc. and iron-containing medications such as ferrous succinate, if you have recently consumed these foods, the undigested and unabsorbed iron in them enters the digestive tract, and under the action of gastric acid as well as intestinal flora, it can produce black ferrous sulphide, which will darken the stools. Generally, after stopping the consumption of such foods and medicines, the black stools will gradually disappear. 2. The appearance of tarry black stools may also mean the appearance of gastrointestinal bleeding, because the blood also contains more iron, the same will be in the intestinal tract to generate ferrous sulfide, the appearance of black stools. Therefore, after finding the black stool, you should go to the gastroenterology department for further examination, such as gastroscopy, enteroscopy, etc., after a clear diagnosis, reasonable and standardized treatment.