Diarrhea after taking metronidazole, belongs to the adverse drug reaction or antibiotic-associated diarrhea, need to stop the drug, regulate the intestinal flora, severe diarrhea can be given antidiarrheal, rehydration and other drug treatment. Metronidazole is an antibiotic mainly used for the treatment of anaerobic infections. Abdominal pain, diarrhea, nausea, vomiting, loss of appetite and other adverse reactions are common after taking the drug. Diarrhea caused by adverse drug reactions can be gradually relieved after stopping the drug. If the diarrhea is severe, oral rehydration salts, montelukast and other drugs. Diarrhea after eating metronidazole also need to be vigilant for antibiotic-associated diarrhea. Refers to the use of antibiotics caused by intestinal flora imbalance, which led to the medical origin of diarrhea. The mechanism of its occurrence for the use of antibiotics after the dysbiosis; antibiotic allergic reactions, toxic effects directly on the intestinal mucosa; pharmacological effects to the intestinal dynamics of the change and so on. For antibiotic-associated diarrhea, oral probiotics such as bifidobacteria, lactobacillus, etc. to regulate the intestinal flora, and at the same time give zinc supplementation to protect the gastrointestinal mucosa treatment. For patients with severe diarrhea, stop metronidazole in time and give antidiarrheal, potassium and fluid replacement treatment to relieve diarrhea and maintain electrolyte and acid-base balance. In short, diarrhea should first go to a professional doctor to find out the cause of the disease, and then targeted treatment, do not take medication, so as not to delay the condition.