Waking up in the morning with bad breath can be caused by physiological factors such as diet or bad habits, or it can be caused by gingivitis, periodontitis, gastritis and other diseases. 1. Physiological factors: If patients eat a lot of garlic, onions and other stimulating foods before going to bed, or go to bed without brushing their teeth in time after eating, the reduction of saliva during sleep will lead to a large number of bacteria or food residues are not decomposed, which will lead to the phenomenon of patients waking up in the morning with bad breath. 2. Pathological factors (1) Gingivitis, periodontitis: gingivitis is usually caused by local plaque in the oral cavity, and the main symptoms of patients are bleeding when brushing teeth, gum hypertrophy, pain, bad breath and other symptoms. In addition, gingivitis can also lead to the symptoms of localized itching and swelling of the gums. (2) Gastritis: Gastritis is mainly caused by the infection of Helicobacter pylori bacteria, and patients will experience epigastric pain, nausea, abdominal distension, vomiting and other symptoms. Since patients with gastritis will experience nausea and vomiting, it will also lead to the manifestation of waking up with bad breath in the morning. (3) Other: other diseases such as pyloric obstruction can also cause patients to wake up with bad breath in the morning. When patients wake up with bad breath in the morning, if it is caused by physiological factors, no treatment is needed. If it is caused by disease, patients should consult a doctor in time and follow the doctor’s instructions for treatment.