Getting up in the morning with bitter mouth odor and phlegm yellow may be caused by bad habits, oral diseases, gastrointestinal diseases, liver and gallbladder diseases, etc. It is recommended to go to the hospital for timely examination and treatment. 1. Often eat odorous food or do not brush your teeth properly will lead to heavy plaque and calculus in the mouth, and it is easy to have bad taste in the mouth. 2. If there are gingivitis and periodontitis in the mouth, the gums will be red, swollen and pus-filled, and there will be bitter breath, bad breath, yellow phlegm and other manifestations. Salivary gland diseases, tumors, etc. will also have this performance. 3. Gastrointestinal dyspepsia, gastric ulcer or sinusitis may cause reflux or bacterial infection in the mouth. 4. Stones and polyps in the liver and gallbladder can also cause bitter breath and halitosis in the mouth. It is recommended to consult a doctor if you have bitter breath, bad breath or yellow phlegm.