Causes of calcium deficiency in infants and children are many, but mainly two factors, one is the continuation of calcium deficiency in the fetal period. Pregnant women’s nutrition is not reasonable, insufficient sunlight exposure, excessive rest caused by excessive fetal growth can lead to fetal calcium deficiency, at birth the child will be easy to panic, sleep restlessness, soft skull, large fontanel, some even appear throat wheezing and convulsions, this is the congenital calcium deficiency. The second type of causes are postnatal factors: 1. Insufficient sunlight exposure in infants and children, insufficient vitamin D production in the body, which affects the absorption of calcium. 2, insufficient intake of vitamin D. Infants and young children eat more natural foods, which contain less vitamin D. They often cannot meet the demand for vitamin D. If they are not supplemented in time, calcium deficiency is easily caused. 3.Insufficient calcium in food or improper calcium-phosphorus ratio, which affects the absorption of calcium. 4, Infants and young children grow fast and have a high demand for vitamin D and calcium, which can easily cause calcium deficiency. 5.Some diseases such as diarrhea and liver and kidney diseases affect vitamin D metabolism and calcium absorption. 6.The oxalate and phytate in certain vegetables and cereals hinder calcium absorption. There are many manifestations of calcium deficiency in infants and young children. Early on, some neuropsychiatric symptoms appear, such as irritability, irritability, sleep disturbance, crying at night, excessive sweating, shaking head during sleep, etc.. Further development causes skeletal changes, such as softening of the skull, square skull, enlarged fontanelle and delayed closure, late teething, cocksucker’s chest, funnel chest, rib-edge ectropion, limb deformity (“O” leg or “X” leg, etc.), flattened pelvis, etc. In addition, calcium deficiency in infants and young children can also cause muscle relaxation, low muscle tone, weakness of the head and neck, backward development of sitting and standing functions, hyperextension of large joints due to ligament relaxation, abdominal bulging due to low muscle tone, abnormal cerebral cortex function affecting intellectual development, indifferent expression, delayed language development, low immunity and easy to develop infections, etc. When it comes to calcium supplementation for infants and children, there are many misconceptions, some people think that all children need calcium supplementation, in fact, this is wrong, we need to know that only the human body needs to supplement calcium deficiency, people who do not need to supplement; some people think that during pregnancy can not take calcium preparations, taking will be detrimental to the development of the child, this idea is also wrong, at present, pregnant women have short daylight exposure, the phenomenon of unreasonable diet is very common, this situation causes pregnant women’s calcium nutrition The calcium supplementation during pregnancy is necessary to prevent calcium deficiency in infants and children. Some parents hope to prevent calcium deficiency in their infants through medication alone, but it is important to know that the main way to prevent calcium deficiency is to obtain calcium through diet and vitamin D, which helps calcium absorption through sunlight exposure. Calcium supplementation through medication alone is not safe and often does not achieve the desired results. There are many parents who believe that calcium deficiency is not good for their children and there is no harm in taking more calcium, but this idea is also wrong. It is important to know that any kind of nutrient deficiency is not okay, and too much is also harmful, so calcium supplementation should be reasonable and have the right method. The correct way to supplement calcium is to first adjust the diet, from the dietary intake of calcium is the most important way to supplement calcium, but also the safest way. When it comes to a reasonable diet, we have to start from pregnancy, or even before pregnancy to adjust our nutritional status, only then can we ensure that children do not have calcium deficiency during the fetal period, that is, no congenital calcium deficiency; after birth, we advocate breastfeeding, and in case of insufficient breast milk, try to choose a formula whose nutritional composition is basically the same as breast milk, and add supplementary food reasonably after 4 to 6 months. While adjusting the diet, it is important to increase the opportunities for outdoor activities and fully enjoy the sunlight to produce sufficient amount of vitamin D in the body to help the absorption of calcium, which, like the diet, should start from the pregnancy. In addition, actively prevent and treat diseases that affect the metabolism and absorption of calcium and phosphorus, such as diarrhea and liver and kidney diseases. On top of this, take appropriate calcium and vitamin D supplements. When choosing calcium preparations, the first thing to consider is safety and security, followed by the production process, solubility, absorption rate and utilization rate.