Question: "I have a friend in prison. He has really bad diabetes and is coughing up blood. What could it be?"
For a person who is in prison, the risk of Tuberculosis (TB) is significant. If he is newly coughing up blood, we have to assume it is TB until proven otherwise. His Diabetes, if not well-controlled, could reduce his immune sytem's ability to fight off the bacteria, therefore increasing the chance that he would get sick from it. If it is not TB, (and we hope it is not), then it could be any other type of pneumonia or many other things. Coughing up blood is always a serious symptoms that should be addressed immediately. Please ask your friend to see the doctor, so he can be evaluated as soon as possible.