Infants taking vitamin D supplements should not take more than 20 μg per day, and the recommended dose is oral vitamin D daily, 400-800 U is preferred. Because long-term use of high doses of vitamin D supplements can easily cause poisoning. The main manifestations of poisoning are thirst, itchy skin, vomiting, diarrhea, frequent urination, anorexia, drowsiness, and abnormal deposition of calcium, which is mainly used to promote calcium absorption and help babies grow and develop. Parents can also supplement vitamin D in other ways, for example, they can let their children get more sunlight, just by exposing their wrists and legs to the sun for 30 minutes a day, they can achieve the purpose of replenishing the vitamin D needed by the body.