Diarrhea at night can cause anxiety and discomfort. Diarrhea is when you have loose, watery stools. Nocturnal diarrhea occurs at night and often disrupts sleep. There are many causes of nighttime urination. You may have only mild diarrhea that will clear up in a day or two. Or you may have chronic nocturnal diarrhea. Chronic diarrhea lasts for four weeks or more and can be a sign of a serious health condition. You should see your doctor in case of severe or chronic diarrhea.