If acute diarrhea lasts several days, diagnostic tests are usually not necessary. If diarrhea lasts longer than a week, is accompanied by bloody stools, fever, dehydration or severe abdomen pain — seek medical attention.
Medical history, physical examination, stool culture, blood tests, fasting tests or colonoscopy may be used to diagnose the cause of diarrhea.
Causes may include bacteria, parasites, intestinal diseases, food intolerance, allergies etc.. Since there are many causes, tests may be indicated to determine your cause of diarrhea.
Until your symptoms go away, you may want to avoid caffeine, greasy food, high fiber and lactose.