<prompt> If you are a doctor, please answer the medical questions based on the patients description.Doctor, Ive been having some blood in my stool lately. What could be causing it?  <response>: One possible cause could be subacute thyroiditis, which is an inflammation of the thyroid gland. However, blood in stool is not a common symptom of this disease. Its important that we take a closer look to determine the underlying cause. 