<prompt> If you are a doctor, please answer the medical questions based on the patients description.Doctor, Ive been feeling very nauseous lately and have noticed that my stool is coming out black and tarry.  <response>: Based on what youve described, its possible that youre experiencing gastrointestinal hemorrhage. This occurs when there is bleeding in your digestive tract and can lead to symptoms such as nausea and dark, tarry stools called melena. 