Is pneumonia serious, and what will happen if it worsens or goes untreated? Severe pneumonia can lead to septic shock and can even be life-threatening. If pneumonia is not treated or not treated thoroughly, it can deteriorate into the following conditions: First, it can cause lung abscesses and empyema, and even lead to pericarditis, meningitis, and more; Second, the infection can enter the bloodstream, causing bacteremia and even septic shock; Third, the patient's continuous high fever can lead to febrile convulsions and even the possibility of coma; Fourth, extensive pneumonia can reduce the function of the alveoli, causing hypoxia and carbon dioxide retention. Hypoxia can affect the function of the nervous system, and patients with severe pneumonia may experience drowsiness, irritability, and even convulsions and coma.