The best time to give calcium supplements to four-year-old babies, most recommend choosing the mornings and evenings of spring and summer, and giving calcium supplements during that time. Because the temperature gradually turns warmer in these two seasons, the baby’s outdoor activity time increases, and the sun can be directly converted into vitamin D after irradiating the skin, and the absorption of calcium is at the best period. In addition to medication calcium supplements, more calcium-rich foods should be given, such as shrimp, milk, eggs, soy products, etc., all rich in calcium. Four-year-old babies who have skeletal changes due to rickets should be accompanied by physical exercises such as chest expansion.