Waking up in the morning with a bitter mouth may be periodontitis, reflux esophagitis, cholecystitis, etc., need to be specifically analyzed. 1. Periodontitis: poor oral hygiene, periodontitis will be manifested as bitter mouth, bad breath, can also be accompanied by bleeding gums and other symptoms. 2. Reflux esophagitis: When suffering from reflux esophagitis, stomach acid will reflux to the esophagus after lying down at night, so bitter mouth may appear in the morning, accompanied by acid reflux, heartburn and other symptoms. 3. Cholecystitis: Bile reflux occurs in cholecystitis, which may lead to bitter mouth in the morning, accompanied by abdominal pain, jaundice and other symptoms. There are many reasons for morning sickness, so it is recommended to consult a doctor in a timely manner to identify the cause of the sickness and avoid delaying the condition.