The clinical symptoms of calcium deficiency in four-month-old children are mainly as follows: first, increased neuroexcitability. Sleep is insubstantial, easy to wake up, and more sweating; second, easy to appear the symptoms of convulsions, but this kind of convulsions usually does not have the change of consciousness, and will not affect the change of respiratory function; third, there will be more movements of the child, often shaking his head and a series of other symptoms. Parents are advised to take the child to the hospital in time and give appropriate treatment under the guidance of the doctor.