The most common cause of red sputum is infection with Klebsiella pneumoniae, a bacterial infection that makes sputum red or brick-red in color and jelly-like, a very common phenomenon. In addition to this cause, there are other causes, such as lobar pneumonia, bronchiectasis, tuberculosis or lung cancer, which can cause red sputum, because the sputum has blood in it. It is necessary to go to the hospital for examination, such as taking chest CT or chest X-ray to make a clear diagnosis, otherwise the simple description of the color of sputum is not very clear for the future diagnosis, or need a special examination to clarify the disease.