Black stool after eating pig’s blood is usually considered that pig’s blood is not thoroughly digested and absorbed inside the intestine, and the iron contained in it is excreted and expressed as black. If black stools are still solved three days after stopping eating pig’s blood, the patient should consider the possibility of bleeding in the stomach or intestines, which can be clarified by a routine stool test plus occult blood test. If the occult blood test is positive, further information is needed to find out if there is epigastric pain or pain around the belly button. If there is epigastric pain or hidden distension in the epigastrium, an electronic gastroscopy is needed to rule out the possibility of bleeding from lesions in the stomach and duodenum. If there is pain around the navel or in the lower abdomen, colonic bleeding needs to be considered and can be clearly diagnosed by performing an e-colonoscopy. In addition, excessive consumption of pig’s blood can also affect the function of the stomach and intestines, so patients are advised to pay attention to a reasonable diet and avoid excessive consumption of pig’s blood.