Besides conducting a physical exam and reviewing your medications, your doctor might order tests to determine what's causing your diarrhea. They include:

  • Blood test. A complete blood count test can help determine what's causing your diarrhea.
  • Stool test. Your doctor might recommend a stool test to determine whether a bacterium or parasite is causing your diarrhea.
  • Flexible sigmoidoscopy or colonoscopy. Your doctor might recommend one of these procedures to look at the lining of your colon and provide biopsies if no cause is evident for persistent diarrhea.

    Both procedures involve using a thin, lighted tube with a lens on the end to look inside your colon.