Bitter mouth during the daytime may be caused by smoking, poor gallbladder function, inflammation of the oral cavity, abnormal gastric function and so on. 1. Smoking: If the pressure is too high, the patient can relieve the pressure by smoking, which will lead to the phenomenon of bitter mouth during the day. 2. Poor gallbladder function: when bitter mouth occurs during the day, it may be caused by poor gallbladder function. Inflammation will lead to bile reflux to the stomach, which will make the secretion of the gallbladder abnormal, and it will lead to the phenomenon of bitter mouth. 3. Poor gastric function: due to poor gastric dynamics, food stays in the stomach and intestines for too long, resulting in bile reflux phenomenon, which can cause bitter mouth and other uncomfortable symptoms. 4. Oral inflammation: when there is periodontitis, lingual inflammation, burning mouth syndrome, etc., may lead to symptoms of bitter mouth. It is recommended that patients go to the hospital in a timely manner, under the diagnosis of the doctor, according to the cause of targeted treatment, pay attention to oral hygiene in daily life, eat less spicy and stimulating food.