Thin sputum is not a sign of improvement, it may be a sign of aggravation of the disease and requires timely medical examination. If sputum becomes thick and thin, it is not a sign of improvement. Improvement should be accompanied by a gradual decrease in sputum until it disappears completely. If the sputum becomes thicker, it may be an aggravation of the disease. On the one hand, it may be caused by the aggravation of the infection, and on the other hand, it may be caused by the sputum not being able to be coughed up in time, and then it collects in the pharynx and the trachea, and then it becomes thicker. However, the progress of the disease cannot be clearly determined by the symptoms, and the results of the examination should be taken into account. It is recommended to consult a doctor for lung X-rays, blood tests, sputum cultures, etc. to determine the progress of the disease, and for the doctor to make a comprehensive assessment of the disease to determine whether it is getting better or not.