Three-month-old babies who can’t lift their heads up may be caused by vitamin D deficiency, growth retardation or other diseases. 1. Vitamin D deficiency: Vitamin D can promote bone growth, if the baby has been in a state of vitamin D deficiency since birth, it may lead to malnutrition, which can lead to the phenomenon of three months unable to lift the head. 2. Growth retardation: some babies may have slower growth and development, which is usually related to heredity or premature birth. If the baby has no other abnormalities, parents can exercise the baby to raise his head. 3. Other diseases: If the baby suffers from metabolic disease, bone disease or endocrine disease, etc., it will affect the baby’s growth and development, thus appearing to lift the head up. There may be other reasons why a three-month-old baby can’t lift his head up, so it is recommended that you go to the hospital in time to improve the examination and clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.