A change from white sputum to yellow sputum may be severe, and a change from purulent sputum to yellow sputum may be a sign of remission, but it is not possible to judge the progress of the disease from the sputum. Whether coughing up yellow sputum is serious or relieved depends on the previous symptoms. If the cough changes from white sputum to yellow sputum, it may be serious, especially for infectious diseases of the lungs, which may be a sign of aggravation of the infection, and if the sputum changes from purulent sputum to yellow thin sputum, it may be relieved, for example, in the case of lung abscesses, etc. However, the above is only a judgment based on the symptoms. However, the above situations are only based on symptoms, and cannot be used as a basis for staging the disease. To determine whether the disease has worsened, it is necessary to consult a doctor in a timely manner for lung X-ray or CT, blood tests, etc., and to observe whether there is any change in the relevant infectious indexes, such as white blood cells, and so on. Therefore, it is recommended to consult a doctor in time, subject to the doctor’s opinion.