Serum calcium is mainly found in human plasma and is composed of three main components: complex calcium, ionized calcium and protein-bound calcium. The serum calcium contained in normal adults is usually 2.03-2.54mmol/L, and the serum calcium contained in children is usually 2.25-2.27mmol/L. The regulation of serum calcium in the human body is mainly regulated by parathyroid hormone, calcitonin, and 1,25-hydroxyvitamin D3, which is manifested in the human body among the liver, bones, and intestines. Abnormal serum calcium levels mean that the body has low parathyroid hormone, abnormal calcium synthesis, and the emergence of certain undesirable liver and kidney diseases, bone diseases, and intestinal diseases, which can cause damage to the body and even endanger life. Once the serum calcium abnormalities need to be alerted, timely examination and treatment.