A one-month-old baby’s low milk intake and lethargy may be caused by physiological or pathological factors, such as sleep deprivation; pathological factors such as encephalitis, meningitis and other infectious diseases of the central nervous system. 1. Physiological factors: the baby may have a lack of sleep, causing the baby to have a prolonged sleep time and reluctance to breastfeeding phenomenon, which is usually an occasional situation. Such babies are generally in good condition and wake up with good spirit and normal growth and development. 2. Pathological factors: when the baby has central nervous system infections such as encephalitis, meningitis, etc., will cause the central nervous system function abnormalities, in addition to decreased appetite, there will be blurred consciousness, lethargy and other neurological symptoms; in addition, the baby has a high fever will also be decreased appetite and lethargy symptoms. One-month-old babies with low milk intake and drowsiness may also have other causes, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.