Baby’s underweight is usually due to malnutrition, lack of sleep, hypothyroidism and other reasons, which can be treated by adjusting lifestyle habits, medication and so on. 1. Malnutrition: Some babies are malnourished due to improper feeding or insufficient gastrointestinal absorption, which leads to malnutrition and underweight. This situation needs to increase the amount of baby food, if necessary, can be treated through extracorporeal nutrition. 2. Lack of sleep: weight may not reach the standard and sleep may also have a certain relationship, it is recommended that parents give the baby to create a quiet, warm and comfortable sleeping environment to increase the baby’s sleep time, improve the quality of sleep. 3. Hypothyroidism: some babies may be due to congenital or acquired insufficient intake of certain nutrients leading to hypothyroidism, this situation may require parents to give the child appropriate iodine supplementation, if necessary, the use of thyroid hormones and other treatment. There are many reasons why a baby’s weight may not reach the standard, once you find that your baby’s weight does not reach the standard, you need to consult a doctor in time, under the guidance of the doctor to find out the cause of the disease, and symptomatic treatment. Another tip, if you need to use drugs need to be used under the guidance of a doctor, do not blindly use drugs.