If children are given too much vitamin D orally or by injection, it will lead to increased absorption of calcium in the small intestine. When the blood calcium continues at a high level, it will excite the sympathetic nerves, which, together with the strong sensitivity of pediatric blood vessel walls to angiotensin, can cause skin vasoconstriction, making it difficult for the body to sweat, resulting in impaired thermoregulation, and the body heat not being radiated and accumulating too much, which in turn causes fever. In the market, there are many kinds of foods fortified with vitamin D, such as milk powder fortified with vitamin D, liquid milk, cream of wheat, etc. The parents are worried about their children’s calcium deficiency and know that they should supplement vitamin D with calcium, so in addition to vitamin D fortified foods, some parents also give their children cod liver oil or vitamin D. However, they do not know that too much vitamin D can cause adverse reactions, and fever is one of the common symptoms. Children are in the growth and development stage, the neurological system is not yet perfect, especially the regulation of the vegetative nervous system is poor, so that the body temperature is susceptible to changes due to various factors. If an excessive amount of vitamin D is given to the child orally or by injection, it will lead to increased absorption of calcium in the small intestine. When the blood calcium continues at a high level, it will excite the sympathetic nerves, which, together with the strong sensitivity of pediatric blood vessel walls to angiotensin, can cause skin vasoconstriction, making it difficult for the body to sweat, resulting in impaired thermoregulation, and the body heat not being radiated and accumulating too much, which in turn causes fever. Fever caused by excessive consumption of vitamin D in children has its own characteristics: body temperature is higher at night than during the day, and the change in body temperature over 24 hours is more than 1℃; the temperature of the limbs is significantly lower than that of the head and trunk; the face is pale, and the skin has little or no sweating; some children also have symptoms such as irritability, thirst, polyuria, and poor nausea. As a parent, once you find that your child has a fever, you should promptly take your child to the hospital for examination. If the fever is caused by excessive vitamin D intake, you should immediately stop supplementing vitamin D. The body temperature can gradually return to normal. Finally, parents are advised that vitamin D and calcium supplements for children should be scientific and should follow medical advice.