Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Diarrhea ?
    ### Response:
    If acute diarrhea lasts 2 days or less, diagnostic tests are usually not necessary. If diarrhea lasts longer or is accompanied by symptoms such as fever or bloody stools, a doctor may perform tests to determine the cause.
                
Diagnostic tests to find the cause of diarrhea may include the following:

    