Vitamin D is a medication used to prevent and treat rickets. Vitamin D, which includes vitamin D2 and D3, is an inactive precursor of vitamin D that is transformed into active vitamin D by exposure of plants and animals to ultraviolet rays of sunlight during survival . Vitamins D2 and D3 have identical actions and uses. Currently commonly used oral vitamin D preparations are: Concentrated cod liver oil drops: each milliliter contains 50,000 units of vitamin A, vitamin D 5,000 units. Ordinary cod liver oil pills: each capsule contains vitamin A 3000 units, vitamin D 300 units. Concentrated cod liver oil pills: each capsule contains 10,000 units of vitamin A and 1,000 units of vitamin. Vitamin D2 pills: each capsule contains 2,100,000 units of vitamin D. Vitamin D3 tablets: each tablet contains Vitamin D310000 units. Iconium capsule: 0-1 years old preparation: each capsule contains 1500 units of vitamin A and 500 units of vitamin D. Preparation for 1 year old and above: each capsule contains 2000 units of vitamin A and 700 units of vitamin D. There are also injectable preparations: vitamin D2 400,000 units/mL, vitamin D3 300,000 units/mL or 600,000 units/mL. So, how to choose between the different preparations? Different preparations should be used depending on the condition of the child and the purpose of use. Prevention of rickets: 2 weeks after the neonatal period, take vitamin D 400 units per day, preterm infants and twin infants its dosage should be doubled in the first 3 months, that is, 800 units per day, and later changed to 400 units per day. 2 years of age after the slowdown of growth, outdoor activities, food diversification, generally not easy to occur rickets, so do not need to add vitamin D. For long-term use of antiepileptic drugs, such as Phenytoin phenobarbital, etc., patients should be supplemented daily, and the use of anti-seizure drugs, such as phenytoin phenobarbital. For long-term use of antiepileptic drugs such as phenytoin, phenobarbital, etc., patients should be supplemented with vitamin D 2000 units per day. This is due to the fact that these antiepileptic drugs accelerate the inactivation of vitamin D in the liver, leading to vitamin D deficiency. Due to the small doses used in prevention, it is more convenient to use cod liver oil drops or cod liver oil pills. In addition, in order to prevent rickets in infants, publicity and popularization work should be done, starting from pregnancy. Pregnant women and breastfeeding mothers pay attention to diet allocation, eat more food rich in vitamin D and calcium and phosphorus, should be more sunshine, after 4~5 months of pregnancy should be added to take calcium tablets and vitamin D400 units. Treatment of rickets: For children with existing vitamin D deficiency rickets, therapeutic doses of vitamin D should be used according to the stage of the disease, and simple vitamin D preparations should be chosen. Cod liver oil containing vitamin A and D is not suitable for the treatment of rickets, because to achieve the therapeutic dosage of vitamin D, due to the amount of vitamin A contained at the same time is too large, which can lead to vitamin A toxicity. Common therapy: initial rickets, daily oral vitamin D5000-10000 units; radical rickets, daily oral vitamin D10,000-20,000 units. All last for 1 month and then change to preventive dosage. Recovery period generally use preventive dosage. Surprise therapy: high-dose vitamin D surprise therapy, generally used only for severe rickets with complications and children who can not take oral. Intramuscular injection of vitamin D2 or D3.3 million units once, and then change to the preventive dose after an interval of 1 month. However, the use of general rickets is not advocated to prevent vitamin D toxicity. It should be emphasized that, due to the influence of our dietary structure, calcium intake from food is insufficient, therefore, in addition to breastfeeding children, vitamin D should be taken at the same time while taking calcium supplements. At present, there are many varieties of calcium supplements on the market, and their calcium content varies greatly, such as calcium carbonate calcium content of 40%, calcium chloride calcium content of 27%, and calcium gluconate calcium content of only 9%. It is advisable to choose the dosage form which is easy to dissolve and convenient to use.