Diarrhea for several days can be caused by improper diet, intestinal infections, non-infectious diseases of the intestines, gastric disorders, pancreatic or hepatobiliary disorders, etc. Prompt medical consultation is recommended. 1. Improper diet: unhygienic diet, allergic food, toxic food, overeating, etc. can cause diarrhea for several days. 2. Intestinal infections: including bacterial infections (e.g. Escherichia coli, Vibrio cholerae, etc.), viral infections (e.g. rotavirus, etc.), fungal infections (e.g. Candida, Aspergillus, etc.), and parasitic infections (e.g. Giardia lamblia, amoeba, etc.). 3. Non-infectious diseases of the intestinal tract: such as irritable bowel syndrome, multiple polyps in the colon, intestinal malignant tumors, etc. Patients may also be accompanied by abdominal pain, bloody stools, fever, emaciation and other symptoms. 4. Gastric diseases: such as gastric cancer, chronic atrophic gastritis, etc., can cause diarrhea due to the reduction of gastric acid; gastrocolic fistula and other diseases can make the stomach contents flow into the intestines too quickly and cause diarrhea. 5. Pancreatic or hepatobiliary diseases: such as chronic liver disease, cholelithiasis and other diseases can make bile discharge decrease, chronic pancreatitis, pancreatic cancer and other diseases can make pancreatic secretion decrease, thus inducing diarrhea. When patients have diarrhea for several days, they should consult a doctor in time to find out the cause of the disease under the doctor’s guidance, and follow the doctor’s instructions if necessary to carry out the corresponding treatment to avoid blind judgment on their own, so as to avoid delaying the condition.