The best time of the day for babies to take vitamin D3 is between meals for better results, and it is recommended to follow medical advice on the specific time and method of taking it. Usually, babies can start taking vitamin D3 from 15 days after birth, which can effectively prevent calcium deficiency in infants and children and promote growth and development. Vitamin D3 can be taken until one year of age or older. vitamin D3 has the effect of promoting calcium absorption, and calcium absorption is best at night, so it is recommended to give your baby vitamin D3 supplements between breakfast and lunch or between lunch and dinner. in addition, you can get more sunlight in your daily life to help vitamin D3 production and absorption. However, if the baby does not have a calcium deficiency, long-term supplementation is not recommended to avoid increasing the gastrointestinal burden and leading to constipation. Therefore, parents are advised to take their babies to the pediatric internal medicine department of a regular hospital for rationalization by a professional doctor after examination.