Diabetes can cause diarrhea, which is a manifestation of chronic complications of diabetes. Autonomic neuropathy in diabetes affects the gastrointestinal autonomic nerves, causing constipation, epigastric fullness, stomach discomfort, and in severe cases, intractable constipation or diarrhea. Typically, patients present with alternating constipation and diarrhea, and may be combined with a feeling of unclean stools or even fecal incontinence. Diarrhea is often unprovoked, and the patient is constipated and may not pass a stool for 5 days or even a week. Suddenly, diarrhea appears, with several stools per day, gradually becoming dilute and watery, and then constipation reappears after diarrhea. Treatment requires blood glucose control and delaying the progression of diabetic autonomic neuropathy. Patients with diarrhea can be treated symptomatically with antidiarrheal drugs, such as loperamide and montelukast, and can also add nerve-nourishing drugs, such as vitamin B1 and methylcobalamin, and can take appropriate probiotic supplements.