Diet pills contain laxative ingredients, and people who take diet pills often experience diarrhea, and the increased number of stools will rub the mucous membrane of the perianal skin, which in turn will cause bleeding in the stool, or it may be that taking diet pills causes dysfunction of the gastrointestinal tract, inducing inflammatory diseases of the gastrointestinal tract, bleeding from gastrointestinal perforations, anal fissures, bleeding hemorrhoids, etc. The severity of the condition varies according to the amount of bleeding and the systemic self-perceived symptoms. Regardless of the cause of the bleeding in the stool, it is recommended to stop taking diet pills immediately and go to the anorectal department of a regular hospital in a timely manner. According to the condition, colonoscopy and routine stool examination should be done to understand the condition of the bleeding stool and the site of bleeding, so as to treat the cause in time.