The primary food for a newborn is breast milk, and if breast milk is insufficient, it needs to be combined with formula. In addition, vitamin and trace element supplements may be needed. A full-term child will receive one injection of vitamin K1 directly after birth, or three in a row if the child is born prematurely. Usually 4 days after birth, vitamin C can be supplemented. 10 days after birth, vitamin A and vitamin D are supplemented, usually 500-1000 IU/d. Around 4 weeks after birth, a physiological period of anemia or anaemia may occur, and iron supplementation may be needed, such as ferrous lactate, which is supplemented with 2 mg/kg for full-term babies, and 3-4 mg/kg per day for preterm babies and children with very low birth weight. Vitamin E and folic acid supplements may be needed if necessary, although this is less common.