The black color of stools after infusion may be caused by a variety of reasons. First of all, we should exclude the causes of diet and oral medications, eating animal liver and blood products can cause black stools, and eating medications containing iron and bismuth can also cause black stools. In addition, you need to check with your doctor to see if there is any medication that will make your stools black. If not, and if you have ruled out dietary and oral medications, you may have upper gastrointestinal bleeding that may lead to a change in the color of your stools. If you usually have pain in the stomach or around the navel, it is recommended to check the stool routine to see if there is any occult blood, it is recommended to carry out stool routine occult blood, gastroscopy and other tests, regular treatment. Usually eat a reasonable diet, do not smoke, alcoholism, do not eat spicy stimulation, greasy products.