I have stomach pain and black stool not tarry just started today hurts occasionally how long should i wait before going to the doctors?

If melena, go NOW...: Melena, by definition, is passage of dark stools stained with denatured blood. As we established in prior healthtap answers, all dark stool is not melena. Your doctor, or even an over-the-counter test that you can purchase, can check to see if your dark stool contains blood. Needed is for you to provide a sample of the dark stool. False positive results can occur based on diet & stool additives.