Normal human blood calcium concentration is maintained at 2.18-2.63 mmol/L. If it is lower than this value, hypocalcemia is considered. Children with long-term insufficient calcium salt intake or impaired absorption will show symptoms related to calcium deficiency, such as poor mental status during the day, irritability, fidgeting, difficulty falling asleep at night, crying after sleep, easy to wake up, excessive sweating; they may also show symptoms of the digestive system, such as paroxysmal abdominal pain, diarrhea, anorexia, paranoia; the muscular and skeletal systems may show cramps, sternal pain, string rib, chicken chest, X-shaped legs, O-shaped legs; Delayed intellectual development, sparse and uneven tooth alignment, thinning hair; poor health and susceptibility to colds, etc. Calcium ion is an important ion in maintaining the normal function of the heart. It is antagonistic to sodium ion in maintaining the normal function of the heart muscle cells, and low calcium ion levels can lead to abnormal heart function.