'Ké xuè' literally combines 'ké' (to cough) and 'xuè' (blood), meaning the medical symptom of coughing up blood—often indicating a serious respiratory or cardiovascular condition. Unlike nosebleeds or gastrointestinal bleeding, this refers specifically to blood expelled from the lungs or bronchial tubes through coughing. It is not used for spitting blood without coughing, nor for vomiting blood (which is 'ǒu xuè').

The term appears primarily in clinical contexts, health reports, or discussions about symptoms. While it can appear in formal writing or spoken medical advice, it is rarely used in casual conversation unless describing a severe health concern. Because it signals possible illness, its use often carries urgency or alarm, and listeners typically respond with concern or prompt action—like seeking medical help.