Waking up in the morning with bitter breath and bad breath may be physiological factors, but also may be the manifestation of certain diseases, such as oral lesions, respiratory system lesions, digestive system lesions 1. Physiological factors: the reason why the morning after waking up will appear the phenomenon of bad breath, first of all, we should consider may be because usually do not pay attention to personal oral hygiene, thus triggering some oral diseases caused by. 2. Pathologic factors: (1) oral lesions: for example, chronic gingivitis, periodontitis, can also lead to the morning when you feel bad breath, bitter; (2) respiratory lesions: the mouth and respiratory tract are connected, certain respiratory diseases, such as colds, inflammation of the respiratory tract, especially chronic bronchitis inflammation of the patient, often coughing, coughing up pus and sputum, will lead to the patient’s mouth in the morning and bitter and smelly. (3) digestive system lesions: the mouth and digestive tract are also connected, some digestive system diseases, such as common chronic gastritis, especially combined with Helicobacter pylori infection or bile reflux, some patients will feel the mouth stinks in the morning, bitter. Since this symptom alone cannot determine the disease, it does not exclude that it is caused by other factors. It is recommended that if physiological causes are ruled out, the patient should consult a doctor in time to clarify the cause of the disease and give targeted treatment.