For a 4-month-old baby, a sleep duration of about 14-16 hours is normal, but there may be individual differences. The number of hours of sleep per day varies by age during childhood. The younger the infant, the more hours of sleep he or she will get. 4 months old infants should sleep between 14-16 hours, but there may be individual differences. If the sleep time is insufficient, and the sleep is accompanied by insubstantial, easily startled, nocturnal crying, and sweating, it is more likely to consider vitamin D deficiency causing calcium malabsorption. Usually, if infants have adequate nutrition, good appetite and digestion, they will develop fast and may have relatively less sleep time. If the overall development of infants is within the normal range and there are no other uncomfortable symptoms, regular review of the child’s development is sufficient. It is recommended that feeding be done at a fixed time and that the sleeping room be of moderate temperature and humidity, with a quiet environment and dim light, to facilitate growth and development.