Eating crayfish stool is black, may be a normal condition, there may also be ulcerative diseases, tumors, blood diseases. 1. Normal: crayfish is generally heavy oil and salt, eat too much will cause gastrointestinal tract stimulation, may appear indigestion and other symptoms, which leads to the color of the stool is deeper than before. If there is no other abdominal discomfort, may be normal, it is recommended to eat a light diet, eat more fruits and vegetables, less spicy and stimulating food. After eating a normal diet, the color of the stool will return to normal. 2. Ulcerative diseases: For example, gastric ulcer, duodenal ulcer, stress ulcer, esophageal ulcer and other diseases may cause upper gastrointestinal bleeding, resulting in black stools in the morning. If black stool persists, it is recommended to go to the hospital for fecal occult blood test and blood test to rule out the possibility of upper gastrointestinal bleeding. If the test is positive or weakly positive, it is recommended to standardize the treatment under the guidance of the doctor. 3. Tumor: for example, esophageal and gastric tumors, tumor erosion and ulcer necrosis will cause bleeding and lead to black stool. 4. Blood diseases: for example, leukemia, hemophilia, thrombocytopenia, etc. can also cause gastrointestinal bleeding, resulting in black stools in the morning. In short, if the stool is black, it is recommended to go to the hospital for examination in time to rule out gastrointestinal bleeding and other conditions.