A 3-month-old baby sleeps about 15 hours a day. 3-month-old babies are more sensitive to light than before and can gradually differentiate between day and night. In general, 3-month-old babies should maintain about 14-15 hours of sleep a day, while some babies sleep longer and may sleep more than 15 hours a day, which is also normal. There are also babies who have a slightly shorter sleep time, but their mental state is good, their appetite is normal, and their growth and development are normal, which is also normal. However, if the baby’s sleep time is too short, accompanied by poor appetite and frequent crying, parents are advised to take their babies to check whether they are calcium deficient as soon as possible, and take calcium supplements to improve the relevant symptoms in time. Before the baby goes to sleep, parents should pay attention to keeping the environment quiet and the light suitable to promote the baby to fall asleep as soon as possible. When taking care of the baby, parents should not change the baby’s natural sleep pattern to avoid affecting the baby’s mood.