Beginning to cough blood. This is perhaps the most alarming and distressing of all symptoms, and will usually send a patient hurrying to their doctor. Coughing blood is obviously a sign of a serious health issue, and should not be ignored even if the amount of blood coughed up seems minor or innocuous. Remember that cancers are best caught in their early stages. If you have been coughing blood for a while and it seems chronic, it is definitely a symptom… the seriousness of which cannot be ignored. The source of the blood can vary depending on the location of the cancer. It can come from the throat or deeper in the respiratory tract, for example, the lungs. It could even come from the stomach.