Calcium deficiency in 7-month-old children is mainly manifested by changes in the nervous system, as follows: 1. Children may be easily irritated, have irritable emotions, have difficulty in falling asleep, sleep insubstantial, and easily wake up and cry after falling asleep, children usually have night sweats, and can appear square cranium. 2, Some children may become anorexic, paranoid, or do not like to eat supplementary food, or suddenly do not want to drink milk. If your child has the above symptoms, you can take him/her to the hospital for a calcium check in the trace elements and give him/her supplements according to the specific situation.