Recently, the “most unreliable physical examination items” widely circulated on the microblogging site in the People’s Daily also bubbled up, one of which is blood calcium to detect calcium deficiency in children, in which many parents traditionally believe that blood tests for trace elements, blood calcium is normal, the child is not calcium deficient, but the answer is that blood calcium is only indicative, but not comprehensive. Let’s first look at what blood calcium is? Calcium is the most abundant inorganic salt in the body, accounting for 1.5% to 2% of body weight, with a total of about 700 to 1400 g. More than 99% of calcium is deposited in bones and teeth. Bone is the largest reservoir of calcium. Blood calcium mainly refers to plasma calcium, which is relatively stable under the regulation and control of various factors in the body. Blood calcium is present in two forms, ionized calcium and bound calcium, each accounting for 50%. The normal value of human blood calcium is 2.25-2.75 mmol/L. Blood calcium level is related to many important functions of the body, and the hormones that play an important role in regulating calcium and phosphorus metabolism and maintaining normal blood calcium concentration are mainly parathyroid hormone, calcitonin and cholecalciferol. Normal blood calcium ≠ no calcium deficiency During childhood, more calcium is needed in the bones due to the demands of growth and development, when calcium from the serum is absorbed and deposited into the bones. However, in early calcium deficiency, if calcium is not supplemented in time, the calcium concentration in the serum is not enough, and a series of adjustments are made to keep the blood calcium within the normal range to prevent the occurrence of hypocalcemic convulsions. It is the bones that provide the calcium for the serum, and it is the bones that contribute their own calcium in order to keep the serum in the normal range. Therefore, at this time, although the blood calcium check is normal, the real situation is that the bones in the child’s body are already deficient in calcium. How can I be sure that my child is indeed deficient in calcium? Whether a child is calcium deficient or not, the first thing to observe is the presence of obvious symptoms of calcium deficiency, such as sweating, excitement, and lack of sleep. A blood test should be performed with reference to blood calcium, blood phosphorus and alkaline phosphatase (AKP) values. Calcium deficiency in children is actually rare, and many are vitamin D deficient. if calcium deficiency is suspected in children, not only blood calcium, blood phosphorus and AKP are taken, so doctors usually prefer to refer to vitamin D, blood calcium, blood phosphorus and AKP together, and also take wrist bone x-ray. The Chinese Nutrition Society recommends a daily dietary supply of calcium 0-6 months Breastfed children 300 mg/day Artificially fed children 400 mg/day 6-12 months 400 mg/day 1-4 years 600 mg/day 4-11 years 800 mg/day 11-18 years 1000 mg/day