Lung cancer bleeding is characterized by blood in sputum in the early stage, coughing up blood in the middle stage, and haemoptysis in the late stage. Specifically, the lesions in the early stage of lung cancer erode small blood vessels, so it is mostly manifested as blood in sputum, and the amount of blood in sputum will gradually increase as the lesion progresses until it manifests as coughing fresh blood. If the treatment is not effective and the lesions in the lung are not effectively controlled, the cancer lesions will erode the large blood vessels in the late stage, which will lead to massive hemoptysis and even life-threatening. Therefore, once you find coughing, coughing sputum or blood in sputum, you should go to hospital immediately for relevant examination, early diagnosis and early treatment.