Calcium supplementation for children is a clichéd topic for doctors and parents, nothing new but still entangled to this day. If asked, “Has your baby taken calcium supplements?” Nine times out of ten, you will say, “Yes.” Parents often say that their children are calcium deficient and that it is only natural to take calcium supplements. So is your child really deficient in calcium? As the name suggests, vitamin D deficiency is the real cause of the disease, which is a chronic nutritional disease with abnormal bone development due to disorders of calcium and phosphorus metabolism caused by vitamin D deficiency. Therefore, we must first clarify whether your child needs calcium or vitamin D supplementation. Vitamin D is rarely found in food, and infants need 400 U of vitamin D daily, most of which depends on sunlight exposure, which converts 7-dehydrocholesterol into vitamin D3 through the skin. 1 square centimeter of skin exposed to sunlight for 3 hours can produce 20 U of vitamin D3. If God does not give a face, a long rainy day, or a bad environment, such as a city with many tall buildings, the sky is full of dust, blocking the sunlight, it is impossible to ensure the normal amount of needs. In addition, parents are worried about their babies going out in the winter to get cold, and in the summer to worry about heatstroke, small babies and delicate skin, easy to be strong sunlight scorching injury, sunshine is more common. Therefore, babies should start taking 400U of vitamin D from 2 weeks to 2 years after birth. This dose is the amount to prevent rickets and will not be poisoned by daily supplementation. As for calcium supplementation, it varies from person to person: 1, breast milk is sufficient, breast-fed children do not need calcium supplementation, because breast milk contains high calcium, calcium and phosphorus ratio is appropriate, good absorption, can meet the daily needs of children. 2, artificial feeding, now the market formula 100ml contains about 40-100mg of calcium, so if the baby can drink a total of more than 500ml a day, plus the calcium in the complementary food, is also enough, do not need to supplement calcium supplements. 3.If your baby does not have the conditions to feed breast milk and formula, then you need to supplement calcium. 4.If your baby is unfortunately suffering from rickets, he/she should take calcium supplements at the same time with higher doses of vitamin D3. Therefore, in general, most children do not need calcium supplements. So how do you know if your baby has rickets? During the infancy period, your child may wake up easily, sweat a lot, ping-pong head, square cranium, rib exostosis, X- and O-shaped legs when walking, late teething, late closure of fontanel, etc. Based on these symptoms, your doctor will do the appropriate tests to diagnose whether your child is in the active stage of rickets. Only children in the active stage need higher doses of vitamin D and appropriate amounts of calcium supplements. Therefore, children with these symptoms must see a doctor instead of taking calcium supplements blindly.