The main reason for bad taste in the mouth is indigestion, and the main reason for indigestion is caused by improper diet structure. If you eat too much greasy food at dinner, overeating or drinking a lot of alcohol, may lead to bad taste in the mouth the next day, this is because the intestinal tract, the peristalsis of the gastrointestinal tract will slow down at night, digestion and absorption will be affected, food into the stomach and gastric acid neutralization but not well digested and absorbed, the taste of the food will be reflected to the mouth will feel very bad. In addition to indigestion, oral odor can be caused by many other reasons: 1, for example, gingivitis, periodontal lesions can also lead to oral odor. 2, diabetes, if poor blood sugar control or even ketoacidosis can also lead to oral odor. 3, for example, renal insufficiency, uremic patients can also be oral odor. 4, the digestive tract itself, such as peptic ulcer or even gastric bleeding patients, the oral cavity has a very unpleasant taste. Patients, the mouth also has a very unpleasant smell. So, oral odor according to the above analysis, pay attention to the diet to improve if it is still not good, it is recommended to go to the hospital for a clear diagnosis.