Not eating for a day and not being hungry is a sign of poor appetite, and there may be digestive diseases such as peptic ulcer, systemic diseases such as hypothyroidism, psychiatric factors such as anorexia nervosa, and drug factors such as erythromycin. 1. Digestive tract diseases. This type is more common, usually accompanied by abdominal pain, belching and other discomforts. The main peptic ulcer with pyloric obstruction, digestive tract tumors, intestinal obstruction, hepatitis, cirrhosis, pancreatitis and so on. 2. Systemic diseases. This kind of possibility is more. Such as fever caused by various types of infections, various types of electrolyte disorders, hypothyroidism, hypoadrenocorticism and other endocrine diseases, as well as severe anemia, vitamin deficiency, uremia and other diseases. 3. Mental factors. Some people have anorexia nervosa due to the presence of mental factors, resulting in poor appetite. 4. Drug factors. Drugs such as aminophylline, digitalis, erythromycin and so on may cause decreased appetite. It can be seen that there are many reasons for poor appetite, and it is necessary to consult a doctor in a timely manner to clarify the cause of the disease under the guidance of the physician, so as not to delay treatment.